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Regional airline

A regional airline is a general classification of airline which typically operates scheduled passenger air service, using regional aircraft, between communities lacking sufficient demand or infrastructure to attract mainline flights. In North America, most regional airlines are classified as "fee-for-departure" carriers, operating their revenue flights as codeshare services contracted by one or more major airline partners. A number of regional airlines, particularly during the 1960s and 1970s, were classified as commuter airlines in the Official Airline Guide (OAG).

Background
Decades before the advent of jet airliners and high-speed, long-range air service, commercial aviation was structured similarly to rail transport networks. In this era, technological limitations on air navigation and propeller-driven aircraft performance imposed strict constraints on the potential length of each flight; some routes covered less than 100 mi.

As such, airlines structured their services along point-to-point routes with many stops between the originating and terminating air terminals. This system of air transportation effectively forced most airlines to be "regional" in nature, but the lack of distinction among carriers soon began to change with the 1929 launch of Transcontinental Air Transport (T-A-T) in the United States. T-A-T's transcontinental "Lindbergh Line" became America's first contiguous coast-to-coast air service, and it ushered in a new era of major airlines expanding to operate networks with large footprints. The development of long-range aircraft operated by flag carriers like British Overseas Airways Corporation and Trans-Canada Airlines further normalized the capability of "far and wide" air travel among the traveling public.

Shifting definition
"Regional airline" is a flexible term whose meaning has changed substantially over time. What it means today is different than how it has been used in the past. For instance, in the United States, around 1960, the term “regional carrier” denoted the smaller eight of the 12 largest carriers, then known as trunk carriers (or trunk airlines or simply trunks). At the time the four biggest airlines in the United States were known as the Big Four, comprising American, United, TWA and Eastern Air Lines. The other eight trunk carriers were Braniff, Capital, Continental, Delta, National, Northeast, Northwest and Western. Since, at the time, none of these eight had a network approaching the scale of the Big Four, they were known as the regional carriers. This was despite the existence, at the time, of 13 smaller United States scheduled carriers known as local service carriers whose service was arguably far more regional than the “regional” trunks.

So when reading historical sources, it’s important to understand that the term "regional airline" has migrated greatly over time. Sometimes the term has been stretched beyond the point of utility. For instance, in a 1983 article about PBA, Provincetown-Boston Airlines, both Air New England and Air Florida are described as regional airlines. At the time, Air New England was a recently-failed turboprop operator in the northeast USA, while Air Florida was a jet carrier flying from Florida to the northeast, to Latin America and Europe. The two airlines had little in common.

Early growth
As flag carriers grew to fill the demand of long-range passenger traffic, new and small airlines found niches flying between short and under-served routes to-and-from major airports and more rural destinations. Through the 1960s and 1970s, war surplus designs (notably, the Douglas DC-3) were replaced by higher-performance turboprop or jet-powered designs like the Fokker F27 Friendship and BAC One-Eleven. This extended the range of the regionals dramatically, causing a wave of consolidations between the now overlapping airlines.

In the United States, regional airlines were an important building block of today's passenger air system. The U.S. Government encouraged the forming of regional airlines to provide services from smaller communities to larger towns, where air passengers could connect to a larger network.

The original regional airlines (then known as "Local service carriers") sanctioned by the Civil Aeronautics Board from 1943 to 1950 include:

 * Allegheny Airlines
 * Arizona Airways
 * Bonanza Air Lines
 * Central Airlines
 * Challenger Airlines
 * Empire Air Lines
 * Florida Airways
 * Lake Central Airlines
 * Mid-West Airlines
 * Mohawk Airlines
 * Monarch Air Lines (merged with Arizona and Challenger to create Frontier in 1950)
 * North Central Airlines
 * Ozark Airlines
 * Parks Air Lines
 * Piedmont Airlines
 * Pioneer Air Lines
 * Southern Airways
 * Southwest Airways (renamed Pacific Air Lines in 1958)
 * Trans-Texas Airways
 * West Coast Airlines
 * Wiggins Airways

A history and study of regional airlines was published by the Smithsonian Institution Press in 1994 under the title Commuter Airlines of the United States, by R.E.G. Davies and I. E. Quastler.

Deregulation era
Since the Airline Deregulation Act of 1978, the US federal government has continued support of the regional airline sector to ensure many of the smaller and more isolated rural communities remain connected to air services. This is encouraged with the Essential Air Service program that subsidizes airline service to smaller U.S. communities and suburban centers, aiming to maintain year-round service.

Although regional airlines in the United States are often viewed as small, not particularly lucrative "no name" subsidiaries of the mainline airlines, in terms of revenue, many would be designated major airline carrier status based on the only actual definition of "major airline," in the United States, the definition from the U.S. Department of Transportation. This definition is based solely on annual revenue and not on any other criterion such as average aircraft seating capacity, pilot pay, or number of aircraft in the fleet. It is common in the U.S. to incorrectly associate aircraft size with the Department of Transportation's designation of major, national, and regional airline. The only corollary is the Regional Airline Association, an industry trade group, defines "regional airlines" generally as "...operat(ing) short and medium haul scheduled airline service connecting smaller communities with larger cities and connecting hubs. The airlines' fleet primarily consists of 19 to 68 seat turboprops and 30 to 100 seat regional jets." To be clear there is no distinction in the Department of Transportation definition of major, national and regional airlines by aircraft size. The definition is based on revenue. The clash of definitions has led to confusion in the media and the public.

1990s–2000s
Beginning around 1985, a number of trends have become apparent. Regional aircraft are getting larger, faster, and are flying longer ranges. Additionally, the vast majority of regionals within the United States with more than ten aircraft within their fleet, have lost their individual identities and now serve only as feeders, to Alaska Airlines, American Airlines, Delta Air Lines, or United Airlines major hubs. Regional aircraft in the US have been getting slightly more comfortable with the addition of better ergonomically designed aircraft cabins, and the addition of varying travel classes aboard these aircraft. From small, less than 50-seat "single-class cabin" turboprop, to turbofan regional jet equipment, present day regional airlines provide aircraft such as the higher capacity CRJ700, CRJ900, CRJ1000 series of aircraft and the somewhat larger fuselage Embraer E-Jets. Some of these newer aircraft are capable of flying longer distances with comfort levels that rival and surpass the regional airline equipment of the past.

In the early 1990s, much more advanced turboprop-powered, fuel efficient, and passenger friendly DC-3 type replacement projects such as the 19 passenger Embraer/FMA CBA 123 Vector and the 34 seat Dornier 328 were undertaken, but met little financial success, partly due to economic downturn in the airline industry resulting from the outbreak of hostilities when Iraq invaded Kuwait. Many of the regional airlines operating turboprop equipment such as Delta's regional sister Comair airlines in the United States set the course for bypassing entirely the regional turboprops as they became the first to transition to an all-jet regional jet fleet. To a lesser extent in Europe and the United Kingdom this transition, to notably the Embraer or Canadair designs, was well advanced by the late  1990s. This evolution towards jet equipment, brought the independent regional airlines into direct competition with the major airlines, forcing additional consolidation.

To improve on their market penetration, larger airline holding companies rely on operators of smaller aircraft to provide service or added frequency service to some airports. Such airlines, often operating in code-share arrangements with mainline airlines, often completely repaint their aircraft fleet in the mainline airline's sub-brand livery. For example, United Express regional airline partner CommutAir branded its entire fleet as United Express. On the other hand, regional airline Gulfstream International Airlines did not brand their aircraft. When Colgan Air was still operating, they branded a handful of aircraft as Colgan Air, but most were branded as Continental Connection, US Airways Express or United Express, with whom it had contractual agreements.

Business model
21st century regional airlines are commonly organized in one of two ways.

Independent model
Operating as an independent airline under their own brand, mostly providing service to small and isolated towns, for whom the airline is the only reasonable link to a larger town. Examples of this are PenAir, which links the remote Aleutian Islands to Anchorage, Alaska, and Mokulele Airlines, which operates in the Hawaiian islands.

Fee-for-departure (contract) model
As an affiliated airline, contracting with a major airline, operating under their brand name (for example, Endeavor Air operates flights under the Delta Connection brand name for Delta Air Lines), and filling two roles: delivering passengers to the major airline's hubs from surrounding towns, and increasing frequency of service on mainline routes during times when demand does not warrant use of large aircraft, known as commuter flights.

One of the first independently owned and managed airlines in the world that rebranded its aircraft to match a larger airline's brand was Air Alpes of France. During 1974, Air Alpes painted its newly delivered short range regional jets in the livery of Air France.

NLM's KLM style branding does however pre-date the Air France efforts though by a number of years.

The success of the "rebranding" or "pseudo branding" of a much smaller airline into the name recognition of a much larger one soon became clear as passenger numbers soared at Air Alpes, and it was soon decided to paint other aircraft such as the Fokker F-27 into full Air France colours as well.

Many airline passengers find sub-branding very confusing, while many other airline passengers are content to think they are on a mainline or flagship airline's aircraft, while in actuality they are far from it. Sub-branding is pretty consistent throughout the airline industry of the United States, with all the regional airlines, mainline airlines, and the regional airline holding companies, as well as the mainline airlines holding companies participating.

Labor relations

On Feb 12th, 2010, a year after the crash of Colgan flight 3407, Frontline premiered its WGA Award-winning exposé on the industry entitled "Flying Cheap". In the program, reporter Miles O'Brien questioned how the impact of low salaries are having on pilot psyches and how safe this could be for the flying public. When asked to respond to the question, Roger Cohen, president of the Regional Airline Association, told Frontline that, "...there are many other people who earn less money than that and work more days in these communities that can afford it and do it and do it responsibly."

Future
The Small Aircraft Transportation System outlined a new vision for regional mobility, based on services built out of small general aviation aircraft and VLJs (very light jets) with advanced automation. This vision failed to materialize due to its primary focus on rural mobility and a lack of clear and viable business case.

With the introduction of air taxi services and very light jets, city pair links to smaller communities lacking regional connections could become more common. This opportunities could become commercially viable with Advanced Air Mobility and the introduction of electric aircraft.

In some parts of the world, regional airlines face competition from high-speed rail and also coach (bus) services with airlines sometimes replacing feeder services through air rail alliances and contracts with bus companies (e.g., Landline between Philadelphia International Airport and Atlantic City International Airport).

Current regional airline brands

 * Aer Lingus Regional
 * Aeromexico Connect
 * Air Canada Express
 * Air Europa Express
 * Air India Regional
 * Alaska Horizon
 * Alaska SkyWest
 * AnadoluJet
 * American Eagle
 * Azul Conecta
 * BA CityFlyer
 * Cayman Airways Express
 * Delta Connection
 * Fiji Link
 * HOP!
 * Iberia Regional
 * J-Air
 * KLM Cityhopper
 * LATAM Express
 * Lufthansa Regional
 * Moçambique Expresso
 * PAL Express
 * Porter Airlines
 * QantasLink
 * TAP Express
 * Tunisair Express
 * United Express
 * Virgin Australia Regional Airlines
 * WestJet Encore
 * WestJet Link

North America
In North America, regional airlines are operated primarily to bring passengers to the major hubs, where they will connect for longer-distance flights on the national airlines also known as flagship carriers. The smallest regional carriers have become known as feeder airlines. The separate corporate structure allows the company to operate under different pay schedules, typically paying much less than their mainline owners.

Many large North American airlines, have established operational relationships with one or more regional airline companies. Their aircraft often use the aircraft livery for the company they are operating flights for. These airlines can be subsidiaries of the major airline or fly under a code sharing agreement or operating through capacity purchase agreements, with the mainline parent company financing the aircraft for the regional airline, and then placing the aircraft with the regional for very little cost. An example would be Envoy Air, which is fully owned by American Airlines Group and does business as American Eagle.

Many of these large regional airlines have joined the lobbying group Regional Airline Association. This association lobbies purely for the financial interest of the corporate bodies it constitutes, not the employees of those airlines.

Canada
In Canada there are a number of regional airlines. Some of them focus on Canadian Arctic and First Nations communities, while others operate regional flights on behalf of a larger carrier, similar to their American counterparts. Some of these airlines and brands include:
 * Air Canada Express operated by Jazz
 * Air Creebec
 * Air Tindi
 * Bearskin Airlines
 * Canadian North
 * Pacific Coastal Airlines
 * Pascan Aviation
 * Perimeter Aviation
 * Porter Airlines
 * Wasaya Airways
 * WestJet Encore (operating for WestJet)

United States
The trend of branding regional airlines to match the mainline airlines, has led to just three major sub-brands in the United States: American Eagle, Delta Connection and United Express. They are the post-deregulation survivors of the multiple bankruptcies and mergers of the major, legacy, mainline airlines.

These regional brands are a form of a virtual airline, with the regional airline paid to staff, operate and maintain aircraft used on flights that are scheduled, marketed and sold by a partner mainline airline. This practice allows the mainline carrier to use outsourced labor at smaller stations, to reduce costs. In 2011, 61% of all advertised flights for American, Delta, United and US Airways were operated by their regional brands. This figure was only 40% in 2000.

Regional airlines
The formerly small regional airlines have grown substantially, through mergers or by the use of a holding company, as pioneered by AMR Corporation in 1982. AMR created the AMR Eagle Holding Corporation which unified its wholly owned American Eagle Airlines and Executive Airlines under one division, but still maintained the regional airlines' operating certificates and personnel separate from each other and American Airlines.

The most significant regional airlines in the United States, are:

Mainline carrier-owned
 * Alaska Air Group
 * Horizon Air
 * American Airlines Group
 * Envoy Air
 * Piedmont Airlines
 * PSA Airlines
 * Delta Air Lines
 * Endeavor Air

Independent contractors
 * Air Wisconsin
 * CommuteAir
 * GoJet Airlines
 * Mesa Airlines
 * Republic Airways
 * SkyWest Airlines

Smaller commuter airlines
The evolution and chronological history of the commuter side of the regional airline industry can be defined by a number of dates prior to the end of the era of airline regulation by the Civil Aeronautics Board of the United States. Among these significant dates are:

 * 1967 – CAB makes exemption for airlines, starting with the local service carrier Allegheny Airlines; to suspend operating a route with large aircraft due to a lack of passenger traffic to do so profitably, provided the airline operating the CAB awarded route substitutes its operation with other equipment and maintains responsibility the route is served. As such this "exemption" allowed the development of the Allegheny Commuter System and the subcontracting of Henson Airlines to fulfill Allegheny's CAB route award obligations.
 * 1969 and before – aircraft falling below the weight of 12,500 lb were considered small aircraft and thus, not subject to the certification requirements of the CAB.
 * 1969 and after – the CAB officially defined airlines with aircraft of no more than 12,500 lb of maximum gross weight as commuter airlines
 * 1972 – relaxations of the CAB regulations permitted commuter aircraft to carry 30 passengers and a payload of 7,500 lb.
 * 1977 – Official list of U.S. Commuter Airlines in the year prior to airline deregulation
 * 1978 – during the sunset of the CAB regulation the size of commuters were permitted to grow to 60 passengers and 18,000 lb of freight.
 * 1978 and onwards the airline industry was officially deregulated by the Airline Deregulation Act of 1978
 * 1981 – the United States governmental lobbying body of this industry, known as the Commuter Airline Association, changes its name to the Regional Airline Association.

List of Commuter Airlines in 1977 Prior to Airline Deregulation:

 * Air Carolina
 * Air Midwest
 * Air New England
 * Air Wisconsin
 * Alaska Aeronautical
 * Altair Airlines
 * Antilles Air Boats
 * Atlantic City Airlines
 * Bar Harbor Airlines
 * Cascade Airways
 * Cochise Airlines
 * Cumberland Airlines
 * Execuair Airlines
 * Florida Airlines
 * Golden West Airlines
 * Metro Airlines
 * Midstate Airlines
 * New England Airlines
 * Pilgrim Airlines
 * Puerto Rico International Airlines
 * Rio Airways
 * Rocky Mountain Airways
 * Royal Hawaiian Airways
 * Scenic Airlines
 * Seaplane Shuttle
 * Sky West Aviation
 * SMB Stagelines
 * Swift Aire Lines
 * Suburban Airlines
 * Transport Catalina Airlines
 * Tyee Airlines
 * Zia Airlines

Some of the lesser known smaller brands used by the regional airlines and their parent companies were:
 * PWExpress, a regional airline brand of the regional airline named Pacific Wings, IATA code (LW) which is owned by Pacific Air Holdings company
 * New Mexico Airlines, a regional airline brand of Pacific Wings, which is owned by Pacific Air Holdings company
 * Nantucket Airlines, a brand operated by regional airline Cape Air which is wholly owned by the regional airline holding company Hyannis Air Service.
 * Ravn Connect, a commuter /air taxi brand operated by the regional airlines owned by the HoTH parent company in association with Corvus Airlines which operates under the Ravn Alaska marketing brand and is also owned by HoTH.

Europe
European regional airlines serve the intra-continental sector in Europe. They connect cities to major airports and to other cities, avoiding the need for passengers to make transfers.

For example, BA CityFlyer a regional subsidiary of British Airways uses the basic Chatham Dockyard Union Flag livery of its parent company and flies between domestic and European cities.

Some of Europe's regional airlines are subsidiaries of national air carriers, though there remains a strong entrepreneurial sector of independents. They are based on business models ranging from the traditional full service airline to low cost carriers. Innovations include one where the passenger is required to join a membership club before being allowed to fly. Some examples of European regional airlines include:

 * Air Dolomiti
 * Air France Hop
 * Air Nostrum
 * Alitalia CityLiner
 * Aurigny
 * BA CityFlyer
 * Blue Islands
 * CityJet
 * Eastern Airways
 * KLM Cityhopper
 * Loganair
 * Lufthansa CityLine
 * TAP Express
 * Twin Jet

Asia
India has many regional carriers operating currently. Some of these operate under the government's UDAN (Regional Connectivity Scheme).
 * India

Note:- Alliance Air is still a state-owned airline, whereas Air India is private.
 * Alliance Air, a former subsidiary of India's former state-owned flag carrier, Air India.
 * FlyBig
 * IndiaOne Air
 * Star Air

 * Thailand
 * Bangkok Airways has won World's Best Regional Airline from Skytrax three years in a row in 2015, 2016 and 2017
 * Thai Smile

Australia
Australia has an association for regional airline, the Regional Aviation of Australia. More than 2 million passengers and 23 million kg of cargo are involved each year.
 * Airlines of Tasmania
 * Airnorth
 * Alliance Airlines
 * FlyPelican
 * Fly Tiwi
 * King Island Airlines
 * QantasLink, the regional arm of Qantas
 * Regional Express Airlines (Rex), the largest regional airline outside of the Qantas group in Australia, servicing routes in several states and territories.
 * Sharp Airlines
 * Skytrans Airlines
 * Virgin Australia Regional Airlines

Former regional airlines
Post airline deregulation, airlines sought added market share and to do this they sought partnerships with regional and small airlines to feed traffic into the airline hub.

Initially these tie ups tended to use small 15 -19 seat aircraft, which did not have a reputation of passenger comfort, or safe reliable operations, by small often under capitalized tiny airline operators.

To create a common tie and what appeared to be seamless to the air traveler, major carriers marketed in advertising and soon had much smaller airlines paint their small and what was often described as puddle-jumper aircraft, in the image and branding colors of the much larger mainline partner. This was to give the appearance of reliability. Over time these regional aircraft grew in size as airline hubs expanded and competition dwindled among the major carriers.

Below is a list of many of the regional brands that evolved when regional airlines were advertised to look like the major airlines.

Marketing brands with regional-type aircraft
The following is a list of former regional marketing brands operated by lesser known airlines, serving airline hub regional routes on behalf of mainline, legacy, major, or large discount carriers in the United States:

 * Air Florida Commuter
 * AirTran JetConnect
 * Allegheny Commuter
 * Aloha Island Air
 * America West Express
 * American Inter-Island
 * AmericanConnection
 * ATA Connection
 * Braniff Express
 * Continental Connection
 * Continental Express
 * Eastern Atlantis Express
 * Eastern Express ops by (AJC) (AMD) (PBA) (PRE)
 * Eastern Metro Express
 * Frontier Commuter (Combs Airways – ITR Airlines)
 * Frontier Express
 * Frontier JetExpress
 * Grand Connection (Alpha Air)
 * MarkAir Express
 * Midway Connection
 * Midwest Connect
 * New York Air Connection
 * Northwest Airlink
 * Ozark Midwest
 * Pan Am Express (an airline formerly known as Ransome Airlines, acquired by Pan Am in 1987)
 * Piedmont Commuter
 * Reno Air Express
 * Republic Express ops by (9E) (XJ) (MQ)
 * Trans World Express
 * TranStar Sky Link
 * TW Express (TWE)
 * TWA Connection
 * US Airways Express, being replaced by American Eagle as US Airways merges with American Airlines
 * Western Express (OO)

Marketing brands with mainline branding / mainline-type aircraft but operated by regional airlines
The following is a list of former marketing brands operated by smaller airlines, but using larger traditionally non-regional-type equipment such as the Boeing 727, Douglas DC9, Fokker F28, Embraer 190 E-jets, or BAE 146, serving airline hub regional routes on behalf of mainline, legacy, major, or large discount carriers, in the United States:
 * Continental Airlines operated by Royale Airlines
 * Continental Jet Express
 * Continental's Houston Proud Express
 * Frontier Airlines operated by Lynx Aviation
 * Frontier Airlines operated by Republic Airlines
 * Northwest Jet AirLink
 * Midwest (ops by Republic Airlines even after Midwest Airlines is shuttered)
 * Pan Am Clipper Connection (Boston-Maine Airways, a true regional airline within the Pan Am Systems airline and transportation conglomerate, tried to run a fully certificated mainline airline as nothing more than a distinct internal marketing brand of a regional airline.)
 * Pan Am Express (1981–1991, consisting of several airlines contracted to operate regional flights on behalf of Pan Am)

title: Regional airline


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Swiss franc

The Swiss franc, or simply the franc (Franken; franc; franco; franc), is the currency and legal tender of Switzerland and Liechtenstein. It is also legal tender in the Italian exclave of Campione d'Italia which is surrounded by Swiss territory. The Swiss National Bank (SNB) issues banknotes and the federal mint Swissmint issues coins.

It is also designated through currency signs Fr. (in German language), fr. (in French, Italian, Romansh languages), as well as in any other language, or internationally as CHF which stands for Confoederatio Helvetica Franc. This acronym also serves as the ISO 4217 currency code, used by banks and financial institutions.

The smaller denomination, a hundredth of a franc, is a Rappen (Rp.) in German, centime (c.) in French, centesimo (ct.) in Italian, and rap (rp.) in Romansh.

The official symbols Fr. (German symbol) and fr. (Latin languages) are widely used by businesses and advertisers, also for the English language. According to ''Art. 1 SR/RS 941.101 of the federal law collection the internationally official abbreviation – besides the national languages – however is CHF'', also in English; respective guides also request to use the ISO 4217 code. The use of SFr. for Swiss Franc and fr.sv. are outdated. As previously indicated Latinate "CH" stands for Confoederatio Helvetica; given the different languages used in Switzerland, Latin is used for language-neutral inscriptions on its coins.

Before the Helvetic Republic
Before 1798, about 75 entities were making coins in Switzerland, including the 25 cantons and half-cantons, 16 cities, and abbeys, resulting in about 860 different coins in circulation, with different values, denominations and monetary systems. However, the origins of a majority of these currencies can be traced to either the French livre tournois (the predecessor of the French franc) or the South German gulden of the 17th century. The new Swiss currencies emerged in the 18th century after Swiss cantons did not follow the pace of depreciations which occurred in France and Germany. However, they mostly existed only in small change as they were little more than community currency, current in one canton but not in the other, and foreign coins like French francs and kronenthalers were more recognized as currency all over Switzerland.

A high-level summary of existing currencies at the end of the 18th century is shown below, including their equivalents in terms of the French écu of 26.67 g fine silver, the South German kronenthaler of 25.71 g fine silver, and Swiss francs of 4.5 g fine silver.

The livre of Bern and most western Swiss cantons like Basel, Aargau, Fribourg, Vaud, Valais, Lausanne, Neuchâtel and Solothurn originated from the French livre tournois.
 * The livre was divided into 20 sols, 10 batzen or 40 kreuzer.
 * After 1690, 30 Bern batzen equated to either
 * a German Reichsthaler (25.984 g fine silver) worth 2 gulden or 120 kreuzer, or
 * a French Louis d'Argent, equivalent to the Spanish dollar (24.93 g fine silver), worth 3 livres tournois or 60 sols.
 * After 1726, the French écu (laubthaler) of $1/100$ g fine silver was valued at 4 livres or 40 batzen (vs 6 livres tournois in France).
 * After 1815, the German kronenthaler (Brabant thaler) of $1/2$ g fine silver was valued at 3.9 livres or 39 batzen (in Neuchâtel, 4.1 livres).
 * This livre or frank of $26 2/3$ écu was the model for the frank of the Helvetic Republic of 1798–1847.
 * Currencies identical to this standard include the Berne thaler, Basel thaler, Fribourg gulden, Neuchâtel gulden, Solothurn thaler and Valais thaler.

Geneva had its own currency, the florin petite monnaie, with $25 5/7$ florins equal to the livre courant. After 1641, the Spanish dollar was worth $1/4$ florins or 3 livres. Afterwards, the écu was valued at $3 1/2$ florins or $10 1/2$ livres, while the kronenthaler was valued at $12 3/4$ florins or $3 9/14$ livres. See also Geneva thaler and Geneva genevoise.

Many currencies of central and eastern Switzerland originated from the South German gulden. It was divided into 40 schilling or 60 kreuzer, and the thaler was worth 2 gulden. After 1690, this gulden was worth $12 3/8$ a Reichsthaler specie, or 12.992 g fine silver. After 1730, the different guilders of Southern Germany and Switzerland fragmented under varying rates of depreciation. The South German gulden, worth $3 15/28$ a Cologne mark (233.856 g) of fine silver, also applied to the Swiss cantons of St. Gallen, Alpenzell, Schaffhausen and Thurgau. The French écu was valued at 2.8 gulden, while the kronenthaler was valued at 2.7 gulden. See St. Gallen thaler.

The cantons of Zurich, Schwyz and Glarus, however, maintained a stronger gulden worth $1/2$ a Cologne mark of fine silver. The French écu was valued at $1/24$ gulden, while the kronenthaler was valued at $1/22$ gulden; see Zürich thaler and Schwyz gulden. On the other hand, the central Swiss cantons of Luzern, Uri, Zug and Unterwalden maintained a weaker gulden vs the South German gulden. The French écu was valued at 3 gulden, while the kronenthaler was valued at $2 1/2$ gulden (see Luzern gulden).

Helvetic Republic to Regeneration, 1798–1847
In 1798, the Helvetic Republic introduced the franc or frank, modelled on the Bern livre worth $2 18/40$ the écu, subdivided into 10 batzen or 100 rappen (centimes). It contained $2 37/40$ grams of fine silver and was initially worth $1/4$ livres tournois or 1.48 French francs.

This franc was issued until the end of the Helvetic Republic in 1803, but served as the model for the currencies of several cantons in the Mediation period (1803–1814). These 19 cantonal currencies were the Appenzell frank, Argovia frank, Basel frank, Berne frank, Fribourg frank, Geneva franc, Glarus frank, Graubünden frank, Luzern frank, St. Gallen frank, Schaffhausen frank, Schwyz frank, Solothurn frank, Thurgau frank, Ticino franco, Unterwalden frank, Uri frank, Vaud franc, and Zürich frank.

After 1815, the restored Swiss Confederacy attempted to simplify the system of currencies once again. As of 1820, a total of 8,000 distinct coins were current in Switzerland: those issued by cantons, cities, abbeys, and principalities or lordships, mixed with surviving coins of the Helvetic Republic and the pre-1798 Helvetic Republic. In 1825, the cantons of Bern, Basel, Fribourg, Solothurn, Aargau, and Vaud formed a monetary concordate, issuing standardised coins, the so-called Konkordanzbatzen, still carrying the coat of arms of the issuing canton, but interchangeable and identical in value. The reverse side of the coin displayed a Swiss cross with the letter C in the center.

Franc of the Swiss Confederation, 1850–present
The Konkordanzbatzen among the Swiss cantons agreeing on an exclusive issue of currency in francs and batzen failed to replace the over 8,000 different coins and notes in circulation. Despite introduction of the first Swiss franc, the South German kronenthaler became the more desirable coin to use in the 19th century, and it was still quoted in pre-1798 currency equivalents. Furthermore, less than 15% of Swiss money in circulation was in local currency, since French and German gold and silver trade coins proved to be more desirable means of exchange. A final problem was that the first Swiss franc was based on the French écu which was being phased out by France in the 19th century.

To solve this problem, the new Swiss Federal Constitution of 1848 specified that the federal government would be the only entity allowed to issue money in Switzerland. This was followed two years later by the first Federal Coinage Act, passed by the Federal Assembly on 7 May 1850, which introduced the franc as the monetary unit of Switzerland.

The Swiss franc was introduced at par with the French franc, at 4.5 g fine silver or $6 2/3$ g = 0.29032 g fine gold (ratio 15.5). The currencies of the Swiss cantons were converted to Swiss francs by first restating their equivalents in German kronenthaler (écu brabant) of $1 1/2$ grams fine silver, and then to Swiss francs at the rate of 7 écu brabant = 40 Swiss francs. The first franc worth $9/31$th the French écu was converted at 1.4597 Swiss francs.

In 1865, France, Belgium, Italy, and Switzerland formed the Latin Monetary Union, in which they agreed to value their national currencies to a standard of 4.5 grams of fine silver or 0.290322 grams fine gold, equivalent to US$1 = CHF 5.1826 until 1934. Even after the monetary union faded away in the 1920s and officially ended in 1927, the Swiss franc remained on that standard until 27 September 1936, when it suffered its sole devaluation during the Great Depression. Following the devaluations of the British pound, U.S. dollar and French franc, the Swiss franc was devalued 30% to 0.20322 grams fine gold, equivalent to US$1 = CHF 4.37295. In 1945, Switzerland joined the Bretton Woods system with its exchange rate to the dollar fixed until 1970.

The Swiss franc has historically been considered a safe-haven currency, with a legal requirement that a minimum of 40% be backed by gold reserves. However, this link to gold, which dated from the 1920s, was terminated on 1 May 2000 following a referendum, making the franc fiat money. By March 2005, following a gold-selling program, the Swiss National Bank held 1,290 tonnes of gold in reserves, which equated to 20% of its assets.

In November 2014, the referendum on the "Swiss Gold Initiative", which proposed a restoration of 20% gold backing for the Swiss franc, was voted down.

In 2024, advocates of Bitcoin began collecting signatures for a referendum that would  include a clause in the Swiss Constitution stating that the Swiss National Bank must hold part of its reserve in Bitcoin. Advocates state that this will restore Swiss neutrality since it will invest in a stateless commodity in the form of Bitcoin rather than foreign government bonds. Advocates go on to say that foreign investment has made Switzerland more reliant on other countries' economies, particularly Germany and the United States.

2011–2014: Big movements and capping

The onset of the Greek sovereign debt crisis resulted in a strong appreciation in the value of the Swiss franc, past US$1.10 (CHF 0.91 per USD) in March 2011, to US$1.20 (CHF 0.833 per USD) in June 2011, and to US$1.30 (CHF 0.769 per USD) in August 2011. This prompted the Swiss National Bank to boost the franc's liquidity to try to counter its "massive overvaluation". The Economist argued that its Big Mac Index in July 2011 indicated an overvaluation of 98% over the dollar, and cited Swiss companies releasing profit warnings and threatening to move operations out of the country due to the strength of the franc. Demand for francs and franc-denominated assets was so strong that nominal short-term Swiss interest rates became negative.

On 6 September 2011, the day after the franc traded at 1.11 CHF/€ and appeared headed to parity with the euro, the SNB set a minimum exchange rate of 1.20 CHF to the euro ('capping' the franc's appreciation), saying "the value of the franc is a threat to the economy", and that it was "prepared to buy foreign currency in unlimited quantities". In response to this announcement the franc fell against the euro from 1.11 to 1.20 CHF, against the U.S. dollar from 0.787 to 0.856 CHF, and against all 16 of the most active currencies on the same day. It was the largest plunge of the franc ever against the euro.

The intervention stunned currency traders, since the franc had long been regarded as a safe haven. The SNB had previously set an exchange rate target in 1978 against the Deutsche mark and maintained it, although at the cost of high inflation. Until mid-January 2015, the franc continued to trade below the target level set by the SNB, though the ceiling was broken at least once on 5 April 2012, albeit briefly.

End of capping
On 18 December 2014, the Swiss central bank introduced a negative interest rate on bank deposits to support its CHF ceiling. However, with the euro declining in value over the following weeks, in a move dubbed Francogeddon   for its effect on markets, the Swiss National Bank abandoned the ceiling on 15 January 2015, and the franc promptly increased in value compared with the euro by 30%, although this only lasted a few minutes before part of the increase was reversed. The move was not announced in advance and resulted in "turmoil" in stock and currency markets. By the close of trading that day, the franc was up 23% against the euro and 21% against the US dollar. The full daily appreciation of the franc was equivalent to $31,000 per single futures contract: more than the market had moved collectively in the previous thousand days. The key CHF interest rate was also lowered from −0.25% to −0.75%, meaning depositors would be paying an increased fee to keep their funds in a Swiss bank account. This devaluation of the euro against the franc was expected to hurt Switzerland's large export industry. The Swatch Group, for example, saw its shares drop 15% (in Swiss franc terms) with the announcements so that the share price may have increased on that day in terms of other major currencies.

The large and unexpected jump caused major losses for some currency traders. Alpari, a Russian-owned spread betting firm established in the UK, temporarily declared insolvency before announcing its desire to be acquired (and later denied rumours of an acquisition) by FXCM. FXCM was bailed out by its parent company. Saxo Bank of Denmark reported losses on 19 January 2015. New Zealand foreign exchange broker Global Brokers NZ announced it "could no longer meet New Zealand regulators' minimum capital requirements" and terminated its business.

Media questioned the ongoing credibility of the Swiss central bank, and indeed central banks in general. Using phrases like "extend-and-pretend" to describe central bank exchange rate control measures, Saxo Bank chief economist Steen Jakobsen said, "As a group, central banks have lost credibility and when the ECB starts QE this week, the beginning of the end for central banks will be well under way". BT Investment Management's head of income and fixed interest Vimal Gor said, "Central banks are becoming more and more impotent. It also ultimately proves that central banks cannot drive economic growth like they think they can". UBS interest rate strategist Andrew Lilley commented, "central banks can have inconsistent goals from one day to another".

Coins before the Helvetic Republic
Coins before 1700 were based on either the French livre tournois system (in Louis d'Argent, Louis d'Or and fractions) or the South German gulden system (in Reichsthalers, florins and fractions). After 1700 Swiss cantonal currencies diverged from the value of the French and German units. However, they mostly existed only in small change as they were a mere community currency, current in one canton but not in the other, and foreign coins like French francs and Brabant dollars were more recognized as currency all over Switzerland.

Coins of the Helvetic Republic
Between 1798 and 1803, billon coins were issued in denominations of 1 centime, $25 5/7$ batzen, and 1 batzen. Silver coins were issued for 10, 20 and 40 batzen (also denominated 4 francs), matching with French coins worth $1/4$, $1/2$ and 1 écu. Gold 16- and 32-franc coins were issued in 1800, also matching with French coins worth 24 and 48 livres tournois.

Coins of the Swiss Confederation
In 1850, coins were introduced in denominations of 1 centime, 2 centimes, 5 centimes, 10 centimes 20 centimes, $1/4$ franc, 1 franc, 2 francs, and 5 francs. The 1 centime and 2 centime coins were struck in bronze; the 5 centimes, 10 centime and 20 centime in billon (with 5% to 15% silver content); and the $1/2$ franc, 1 franc, 2 franc and 5 franc in .900 fine silver. Between 1860 and 1863, .800 fine silver was used, before the standard used in France of .835 fineness was adopted for all silver coins except the 5 francs (which remained .900 fineness) in 1875. In 1879, billon was replaced by cupronickel in the 5 centime and 10 centime coins and by nickel in the 20 centime piece. Gold coins in denominations of 10, 20, and 100 francs, known as Vreneli, circulated until 1936.

Both world wars only had a small effect on the Swiss coinage, with brass and zinc coins temporarily being issued. In 1931, the mass of the 5 franc coin was reduced from 25 grams to 15, with the silver content reduced to .835 fineness. The next year, nickel replaced cupronickel in the 5 centime and 10 centime coins.

In the late 1960s, the prices of internationally traded commodities rose significantly. A silver coin's metal value exceeded its monetary value, and many were being sent abroad for melting, which prompted the federal government to make this practice illegal. The statute was of little effect, and the melting of francs only subsided when the collectible value of the remaining francs again exceeded their material value.

The 1 centime coin was still produced until 2006, albeit in ever decreasing quantities, but its importance declined. Those who could justify the use of 1 centime coins for monetary purposes could obtain them at face value; any other user (such as collectors) had to pay an additional four centimes per coin to cover the production costs, which had exceeded the actual face value of the coin for many years. The coin fell into disuse in the late 1970s and early 1980s, but was only officially fully withdrawn from circulation and declared to be no longer legal tender on 1 January 2007. The long-forgotten 2 centime coin, not minted since 1974, was demonetized on 1 January 1978.

The designs of the coins have changed very little since 1879. Among the notable changes were new designs for the 5 francs coins in 1888, 1922, 1924 (minor), and 1931 (mostly just a size reduction). A new design for the bronze coins was used from 1948. Coins depicting a ring of stars (such as the 1 franc coin seen beside this paragraph) were altered from 22 stars to 23 stars in 1983; since the stars represent the Swiss cantons, the design was updated when in 1979 Jura seceded from the Canton of Bern and became the 23rd canton of the Swiss Confederation.

The 10 centime coins from 1879 onwards (except the years 1918–19 and 1932–1939) have had the same composition, size, and design to present and are still legal tender and found in circulation. For this, the coin entered the Guinness Book of Records as the oldest original currency in circulation.

All Swiss coins are language-neutral with respect to Switzerland's four national languages, featuring only numerals, the abbreviation "Fr." for franc, and the Latin phrases Helvetia or Confœderatio Helvetica (depending on the denomination) or the inscription Libertas (Roman goddess of liberty) on the small coins. The name of the artist is present on the coins with the standing Helvetia and the herder.

In addition to these general-circulation coins, numerous series of commemorative coins have been issued, as well as silver and gold coins. These coins are no longer legal tender, but can in theory be exchanged at face value at post offices, and at national and cantonal banks, although their metal or collectors' value equals or exceeds their face value.

Banknotes
In 1907, the Swiss National Bank took over the issuance of banknotes from the cantons and various banks. It introduced denominations of 50, 100, 500 and 1000 francs. 20-franc notes were introduced in 1911, followed by 5-franc notes in 1913. In 1914, the Federal Treasury issued paper money in denominations of 5, 10 and 20 francs. These notes were issued in three different versions: French, German and Italian. The State Loan Bank also issued 25-franc notes that year. In 1952, the national bank ceased issuing 5-franc notes but introduced 10-franc notes in 1955. In 1996, 200-franc notes were introduced whilst the 500-franc note was discontinued.

Nine series of banknotes have been printed by the Swiss National Bank, seven of which have been released for use by the general public, the fourth and seventh being reserved and never issued. The sixth series from 1976, designed by Ernst and, depicted persons from the world of science. This series was recalled on 1 May 2000 and is no longer legal tender, but notes can still be exchanged for valid ones of the same face value at any National Bank branch or authorized agent, or mailed in by post to the National Bank in exchange for a bank account deposit. The exchange program originally was due to end on 30 April 2020, after which sixth-series notes would lose all value. As of 2016, 1.1 billion francs' worth of sixth-series notes had not yet been exchanged, even though they had not been legal tender for 16 years and only 4 more years remained to exchange them. To avoid having to expire such large amounts of money in 2020, the Federal Council (cabinet) and National Bank proposed in April 2017 to remove the time limit on exchanges for the sixth and future recalled series. As of 2020, this proposal was enacted, so old banknote series will not expire.

The seventh series was printed in 1984, but kept as a "reserve series", ready to be used if, for example, wide counterfeiting of the current series suddenly happened. When the Swiss National Bank decided to develop new security features and to abandon the concept of a reserve series, the details of the seventh series were released and the printed notes were destroyed. The eighth series of banknotes was designed by around the theme of the arts and released starting in 1995. In addition to its new vertical design, this series was different from the previous one on several counts. Probably the most important difference from a practical point of view was that the seldom-used 500-franc note was replaced by a new 200-franc note; this new note has indeed proved more successful than the old 500-franc note. The base colours of the new notes were kept similar to the old ones, except that the 20-franc note was changed from blue to red to prevent a frequent confusion with the 100-franc note, and that the 10-franc note was changed from red to yellow. The size of the notes was changed as well, with all notes from the eighth series having the same height (74 mm), while the widths were changed as well, still increasing with the value of the notes. The new series contain many more security features than the previous ones; many of them are now visibly displayed and have been widely advertised, in contrast with the previous series for which most of the features were kept secret.

All banknotes are quadrilingual, displaying all information in the four national languages. With the eighth series, the banknotes depicting a Germanophone person have German and Romansch on the same side as the picture, whereas banknotes depicting a Francophone or an Italophone person have French and Italian on the same side as the picture. The reverse has the other two languages.

When the fifth series lost its validity at the end of April 2000, the banknotes that had not been exchanged represented a total value of 244.3 million Swiss francs; in accordance with Swiss law, this amount was transferred to the Swiss Fund for Emergency Losses in the Case of Non-insurable Natural Disasters.

In February 2005, a competition was announced for the design of the ninth series, then planned to be released around 2010 on the theme "Switzerland open to the world". The results were announced in November 2005. The National Bank selected the designs of Swiss graphic designer Manuela Pfrunder as the basis of the new series. The first denomination to be issued was the 50-franc note on 12 April 2016. It was followed by the 20-franc note (17 May 2017), the 10-franc note (18 October 2017), the 200-franc note (15 August 2018), the 1000-franc note (5 March 2019), and the 100-franc note (12 September 2019).

All banknotes from the eighth series were withdrawn on 30 April 2021, but, like banknotes of the sixth series withdrawn in 2000, remain indefinitely redeemable at the Swiss National Bank.

Circulation
The Swiss franc is the currency and legal tender of Switzerland and Liechtenstein and also legal tender in the Italian exclave of Campione d'Italia. Although not formally legal tender in the German exclave of Büsingen am Hochrhein (the sole legal currency is the euro), it is in wide daily use there; with many prices quoted in Swiss francs. The Swiss franc is the only version of the franc still issued in Europe.

As of March 2010, the total value of released Swiss coins and banknotes was 49.664 billion Swiss francs.

Combinations of up to 100 circulating Swiss coins (not including special or commemorative coins) are legal tender; banknotes are legal tender for any amount.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Swiss franc


text:
List of twins

This is a list of notable twins, siblings resultant from a multiple birth.

Actors

 * Kaya and Sarp Akkaya (1980–)
 * Shawn and Aaron Ashmore (1979–)
 * Conrad (1923–2013) and Bonar Bain (1923–2005)
 * Gayle and Gillian Blakeney (1966–)
 * Billy Mauch (1921–2006) and Bobby Mauch (1921–2007)
 * The Borden Twins, Marilyn (1932–2009) and Rosalyn (1932–2003)
 * Julie and Clare Buckfield (1976–)
 * Louis and Carlos Campos, The Fabulous Wonder Twins (1967–)
 * Charlie and Max Carver (1988–)
 * Manpei and Shinpei Takagi (1985–)
 * Andrew and Steven Cavarno (1992–)
 * Dennis (1934–1991) and Phillip Crosby (1934–2004)
 * Brittany and Cynthia Daniel (1976–)
 * Angela and Maureen Deiseach (1972–)
 * The Dolly Sisters, Rosie (1892–1970) and Jenny (1892–1941)
 * Melanie and Martina Grant (1971–)
 * Lindsay and Sidney Greenbush (1970–)
 * Deidre and Andrea Hall (1947–)
 * Pili y Mili (1947–)
 * Jon and Dan Heder (1977–)
 * Jill and Jacqueline Hennessy (1968–)
 * Linda and Terry Jamison (1965–)
 * Brent and Shane Kinsman (1997–)
 * Camille and Kennerly Kitt
 * Gary and Larry Lane (1975–)
 * Mirtha (1927–) and Silvia Legrand (1927–2020)
 * Spencer and Peyton List (1998–)
 * Jason and Jeremy London (1972–)
 * Frankie and George McLaren (1997)
 * David and Anthony Meyer (1972–)
 * Tony and Kelly L. Moran (1957–)
 * Markieff and Marcus Morris (1989–)
 * Tia and Tamera Mowry (1978–)
 * Erin and Diane Murphy (1964–)
 * Mary-Kate and Ashley Olsen (1986–)
 * Jeni and Kyndi Niquette (1988–)
 * Rachel and Amanda Pace (2000–)
 * Pier Angeli (1932–1971) and Marisa Pavan (1932–2023)
 * Ryan and Kyle Pepi (1993–)
 * James and Oliver Phelps (1986–)
 * Raymond and Richard Gutierrez (1984–)
 * Connie and Cassie Powney (1983–)
 * Kathryn and Megan Prescott (1991–)
 * Felix and Dominic Roco (1989–)
 * Giovanni and Marissa Ribisi (1974–)
 * Camilla and Rebecca Rosso (1994–)
 * Liz and Jean Sagal (1961–)
 * Keith and Kevin Schultz (1953–)
 * Jason and Kristopher Simmons (2002–)
 * Jason and Randy Sklar (1972–)
 * Gabriela and Daniela Spanic (1973–)
 * Dylan and Cole Sprouse (1992–)
 * Don and Dan Stanton (1952–)
 * Elliott and Luke Tittensor (1989–)
 * David and Nicholle Tom (1978–)
 * Harry and Luke Treadaway (1984–)
 * Blake and Dylan Tuomy-Wilhoit (1990–)
 * Keaton and Kylie Rae Tyndall (1992–)
 * Lauren and Loraine Vélez (1964–)
 * Lee and Lyn Wilde (1922–2015 & 2016)

Artists

 * Dean and Dan Caten (1964–)
 * Os Gêmeos (1974–)
 * Tim (1939–2006) and Greg Hildebrandt (1939–)
 * Masashi and Seishi Kishimoto (1974–)
 * Moses (1899–1974) and Raphael Soyer (1899–1987)
 * Doug and Mike Starn (1961–)
 * Jerome Witkin and Joel-Peter Witkin (1939–)
 * Anton Pieck (1895-1987) and Henri Pieck (1895-1972)

Authors and writers

 * Julius (1909–2000) and Philip Epstein (1909–1952)
 * Julia DeVillers and Jennifer Roy
 * Matthew and Michael Dickman (1975–)
 * Austin and Lev Grossman (1969–)
 * Alex and Brett Harris (1988–)
 * Linda and Terry Jamison (1965–)
 * Eppie Lederer (1918–2002) and Pauline Phillips (1918–2013), née Esther Pauline Friedman and Pauline Esther Friedman; professionally known, respectively, as Ann Landers (from 1955) and Abigail Van Buren/Dear Abby
 * Ross (1925–1975) and Norris McWhirter (1925–2004)
 * Anthony (1926–2001) and Peter Shaffer (1926–2016)
 * Agnes (1843–1926) and Margaret Smith (1843–1920)
 * Brittany and Brianna Winner (1995)

Businesspeople

 * David and Frederick Barclay (1934–)
 * Randolph Apperson Hearst and David Whitmire Hearst
 * Bill and Bob Meistrell
 * Cameron and Tyler Winklevoss (born 1981)
 * Freelan Oscar Stanley and Francis Edgar Stanley

Comedians

 * Lucas and Marcus Dobre (1999-)
 * Ethan and Grayson Dolan (1999–)
 * Jim (1941–2008) and Jon Hager (1941–2009)
 * Luke and Jai Brooks, from The Janoskians (1995–)
 * Hodgetwins (1974–)
 * Kenny and Keith Lucas (1985–)
 * Veronica and Vanessa Merrell (1996–)
 * Randy and Jason Sklar (1972–)
 * Jools and Lynda Topp (1958-)

Criminals

 * Ursula and Sabina Eriksson
 * Albert (1857–1937) and Ebenezer Fox (1857–1926)
 * June (1963–) and Jennifer Gibbons (1963–1993)
 * Carey Dean Moore and David Moore
 * Jasmiyah and Tasmiyah Whitehead (1993–)
 * Jeena and Sunny Han (1974–)
 * Ronnie (1933–1995) and Reggie Kray (1933–2000)
 * Paul and Chris Dawson (1948–)

Twins in dance

 * Peter Frame (1957–2018) and Paul Frame, (1957–) ballet dancers
 * Les Twins Laurent and Larry Nicolas Bourgeois, French Hip Hop dancers, winners of 2017 World of Dance

Filmmakers

 * Nicola and Teena Collins (1978–)
 * John (1913–1985) and Roy Boulting (1913–2001)
 * Allen and Albert Hughes (1972–)
 * George (1942–2011) and Mike Kuchar (1942–)
 * Gary and Larry Lane (1975–)
 * John Lasseter (1957–)
 * Mark and Michael Polish (1970–)
 * Stephen and Timothy Quay (1947–)
 * Jen and Sylvia Soska (1983–)
 * Matt and Ross Duffer (1984–)

Models

 * Shane and Sia Barbi (1963–)
 * Derek and Keith Brewer (1973–)
 * Kyle and Lane Carlson (1978–)
 * Ava and Leah Clements (2010–)
 * Richard and Raymond Gutierrez (1984–)
 * Monique and Ingrid Kavelaars (1971–)
 * Diane and Elaine Klimaszewski (1971–)
 * Gary and Larry Lane (1975–)
 * Spencer and Peyton List (1998–)
 * Kristina and Karissa Shannon (1989–)
 * Renee and Rosie Tenison (1968–)

Music

 * Joshua and Jacob Kiszka, members of Greta Van Fleet
 * Alejandra and Claudia Deheza of the band School of Seven Bells
 * Veronica and Vanessa Merrell, singers, songwriters and YouTubers
 * Natalie and Nicole Albino, members of Nina Sky
 * Jay (John) and Michael Aston (1957–), of Gene Loves Jezebel (1980–1989; 1995–1997)
 * Miko and Yumi Bai of By2
 * Didem and Sinem Balık, opera singers
 * George and Jack Barnett, members of These New Puritans
 * David Michael and Isabella "Bunny" Bennett, members of Steam Powered Giraffe
 * Mike and Pete Bishop, members of The Bishops
 * Anders and Jonas Björler, members of At the Gates and The Haunted
 * Gayle and Gillian Blakeney (1966–), of The Monitors and The Twins
 * Claire and Antoinette Cann, piano duo
 * Brian and Brandon Casey, members of Jagged Edge
 * Jamie and Vincent Cavanagh, members of Anathema
 * Andrew and Brian Chaplin (1990–), members of South African-based electro duo Locnville
 * ChoA and Way of Crayon Pop
 * Alex and Nels Cline (1956–), avant-garde musicians
 * Keven "Dino" (1974–2003) and Solomon "Shazam" Conner (1974–), members of H-Town
 * Andraé (1942–2015) and Sandra Crouch (1942–), gospel singers
 * Katie and Allison Crutchfield, members of P.S. Eliot
 * Cherie Currie and Marie Currie, singers
 * Kelley and Kim Deal, members of The Breeders
 * Aaron and Bryce Dessner, members of The National
 * Tom and David Farmer, members of Blackfoot Sue
 * Lamb and Lynx Gaede, members of Prussian Blue
 * Marge (1948–1996) and Mary Ann Ganser (1948–1970), members of The Shangri-Las
 * Robin (1949–2012) and Maurice Gibb (1949–2003), members of the Bee Gees
 * Paweł and Łukasz Golec, members of Golec uOrkiestra
 * Matt and Luke Goss (29 September 1968–), members of Bros
 * John and Edward Grimes (1991–), of Jedward
 * Jim and Jon Hager, country duo Hager Twins
 * Tim and Phil Hanseroth, members of Brandi Carlile's band
 * Christoph and Anton Hochheim, members of The Depreciation Guild
 * Rommel and Robert Hinds-Grannum, hip-hop duo A-Game
 * Ryu Hwa-young of T-ara and Ryu Hyo-young of Coed School (1993–)
 * Warattha and Charattha Imraporn (a.k.a. Noey and Jam), Thai pop duo Neko Jump
 * Monica and Gabriela Irimia (1982–), pop duo The Cheeky Girls
 * Emi and Yumi Ito (1941–), pop duo The Peanuts
 * Yusuke and Hisato Izaki, members of Flame
 * Ryan and Gary Jarman (1980–) members of The Cribs
 * Kwangmin and Youngmin Jo of Boyfriend (1995–)
 * Ben and James Johnston, members of Biffy Clyro
 * Len and Rin Kagamine, members of Vocaloid
 * Herbert and Harold Kalin, the Kalin Twins
 * Marianna and Stephanie Kapsetaki (1991–), piano duo
 * Bill and Tom Kaulitz (1989–), members of Tokio Hotel
 * Ellen and Alice Kessler, entertainers
 * Heather and Jennifer Kinley, country music duo The Kinleys
 * Felisha and Fallon King, members of Cherish
 * Jeni and Kyndi Niquette, pop rock duo Jen and Kat
 * Camille and Kennerly Kitt, harp duo The Harp Twins
 * Marcus and Martinus Gunnarsen, pop duo Marcus & Martinus
 * Rafi and Sevan Kirder (1980–), members of Red Shamrock and ex-members of Eluveitie
 * Ryan and Dan Kowarsky, duo RyanDan
 * Supachaya Lattisophonkul and Pailin Rattanasangsatian (a.k.a. Bell and HwaHwa), Thai pop duo China Dolls
 * Remy and Pascal Le Boeuf, jazz duo Le Boeuf Brothers
 * Nathan and Matthew Leone, members of Madina Lake
 * Sari and Romy Lightman, members of Tasseomancy
 * Evan and Jaron Lowenstein, duo Evan and Jaron
 * Edele Barrett and Keavy Lynch (1979–), members of B*Witched
 * Peggy and Patsy Lynn, The Lynns
 * Megan and Liz Mace, aka Megan & Liz
 * Benji and Joel Madden (1979–), members of Good Charlotte and The Madden Brothers
 * Sam and Amanda Marchant, pop duo Samanda
 * Michael and John McGlynn (1964–), directors of Anúna
 * Wendy and Susannah Melvoin (1964–), singers and former members of Prince's backup band The Revolution
 * Jacob and Joshua Miller, members of Nemesis Rising
 * Gabriela and Mihaela Modorcea (1985–), duo Indiggo
 * Alanis and Wade Morissette (1974–), singer/songwriters
 * Sakamoto Naoya and Sakamoto Kazuya, of On/Off
 * Christina and Michelle Naughton, piano duo
 * Gunnar and Matthew Nelson, members of band Nelson
 * Miriam and Olivia Nervo, members of NERVO
 * Peter and Paul Okoye, members of P-Square
 * Jacob and Joshua Olds, members of Family Force 5
 * Ferhan & Ferzan Önder, piano duo
 * Lisa and Jessica Origliasso, pop duo The Veronicas
 * Simone and Amedeo Pace, members of Blonde Redhead
 * Charles (1948–) and John Panozzo (1948–1996), members of Styx
 * Güher and Süher Pekinel, piano duo
 * Mary and Geraldine Peppin, piano duo
 * John and Joshua Pritchard, members of Ruin/Renewal and Brother & Co.
 * Tegan and Sara Quin (1980–), members of indie music duo Tegan and Sara
 * Charlie and Craig Reid, folk duo The Proclaimers
 * John Len Ruela and Len John Ruela Pearce (1991–), members of Justice Crew
 * Paul (1948–1992) and Barry Ryan (1948–), formed the group Paul and Barry Ryan
 * Gabriel and Michael Saalfield, The Royce Twins, singer songwriters of Australia
 * Lee and Tyler Sargent, members of Clap Your Hands Say Yeah
 * Keith and Kevin Schultz, members of Keith, Kevin and Air
 * Denny and Kenny Scott, members of Swirl 360
 * Walter and Wallace "Scotty" Scott, members and lead singers of The Whispers
 * Tom and Dan Searle, members of Architects
 * Toni and Trisha Sherwood, members of 11:30
 * Stuart and James Steele, members of Exit Ten
 * Ani and Nia Sulkhanishvili (1988–), piano duo
 * Daniel ("Dan") and Eric Tadros, members of Tadros
 * Anastasiya and Maria Tolmachevy, child singers; won the Junior Eurovision Song Contest
 * Gyða and Kristín Anna Valtýsdóttir, former members of múm
 * Janice and Jill Vidal, singers
 * Mona and Lisa Wagner, members of The MonaLisa Twins
 * Chandra and Leigh Watson, members of The Watson Twins
 * Andrew and David Williams, members of The Williams Brothers
 * Andy and Jez Williams, members of Doves
 * Marvin and Carvin Winans (1958–)
 * Ben and Zach Yudin, members of Cayucas
 * Alex and Gregg Chamberlain, Twin duo called New Horizon singers, songwriters and Tiktokers
 * Ben and Alex Moore, members of Oliver Riot
 * Sukriti Kakar and Prakriti Kakar, Indian playback singers
 * Wyatt and Fletcher Shears, members of The Garden
 * Kenji and Koji Mihara, members of Frederic (band)
 * Xion, a member of Oneus, and Dongmyeong, a member of Onewe

Politicians

 * Barbara Bush and Jenna Bush Hager (1981–)
 * Julian and Joaquin Castro (1974–)
 * Mariana Mortágua and Joana Mortágua (1986) Portuguese Politicians and daughters of Camilo Mortágua
 * Angela and Maria Eagle, British MPs and members of the Shadow Cabinet.
 * Jaynet and Joseph Kabila (1971–)
 * Jarosław (1949–) and Lech Kaczyński (1949–2010)
 * Jerry Kilgore and Terry Kilgore (1961–)
 * Nechirvan Barzani (1966–) (2nd President of Kurdistan Region) and Dilovan Barzani (1966‒2018)

In reality television

 * Tony and John Alberti (1986–)
 * Natalie and Nadiya Anderson (1986–)
 * Amanda and Michelle Babin (1988–)
 * Isabella and Sofia Bliss (1998–)
 * Igor (1949–2022) and Grichka Bogdanoff (1949–2021)
 * Thomas and Stephen Buell (1992–)
 * Shawn and Claire Buitendorp (1990–)
 * Bennett and Winston Butterfield
 * Dylan and Taylor Cash
 * Jana and John-David Duggar (1990–)
 * Jedidiah and Jeremiah Duggar (1998–)
 * Haley and Emily Ferguson (1992–)
 * Torian and Tre Fields (1992–)
 * Roxanne and Nicole Frilot (1983–)
 * Cara and Madelyn Gosselin (2000–)
 * Cindy and Mindy Hall (1974–)
 * Cece and Cate Hamill (2012–)
 * Ron and Richard Harris (1953–2014, 1953–)
 * Abby and Brittany Hensel (1990–)
 * Elza and Nellie Jenkins (1992–)
 * Leigh and Leslie Keno (1957–)
 * Gary and Larry Lane (1975–)
 * Seoeon and Seojun Lee (2013–)
 * Allie and Lexi Kaplan (1993–)
 * Sam and Amanda Marchant (1988–)
 * Chris and Josh Martinez (1987–)
 * Dario and Raphy Medrano (1992–)
 * Adria Montgomery-Klein and Natalie Montgomery-Carroll (1974–)
 * Skyler and Spencer Nick (1992–)
 * Becky and Jessie O'Donohue (1980–)
 * Ji & Le Otun
 * Kristina & Kamila Podvisotskaya
 * Zach and Jeremy Roloff (1990–)
 * GinaMarie and AnnaMarie Russo (1986–)
 * Darcey and Stacey Silva (1974–)
 * Drew and Jonathan Scott (1978–); see also Property Brothers, the series and media franchise featuring the pair
 * Aliannah and Aleeah Simms (2009–)
 * MeMe & Key Vickers
 * Danielle and Gabrielle Victor (1988–)
 * Adam & Cory Zinker (1992–)
 * Sugar and Spice, drag personas of Cooper and Luca Coyle (1998-)

Religion

 * Jacob and Esau, sons of Isaac
 * Pharez and Zerah, sons of Judah

Royalty

 * Antiochus XI Epiphanes (124/109 BCE – 93 BCE) and Philip I Philadelphus (124/109 BCE – 83 or 75 BCE)
 * Alexander Helios (b. 40 BCE) and Cleopatra Selene II (40 BCE–6 CE)
 * Ramon Berenguer II (1053/54–1082) and Berenguer Ramon II (1053/54–1097/99)
 * James II of Scotland (1430–1460) and Alexander Stewart, Duke of Rothesay (1430–1430)
 * Princess Louise Élisabeth of France (1727–1759) and Princess Henriette of France (1727–1752)
 * Philipp, Landgrave of Hesse (1896–1980) and Prince Wolfgang of Hesse (1896–1989)
 * Prince Christoph of Hesse (1901–1940) and Prince Richard of Hesse (1901–1969), younger brothers of Philipp and Wolfgang
 * Princess Aisha and Princess Sara bint Al Faisal (1997–)
 * Prince Alexander and Prince Philip of Yugoslavia (1982–)
 * Prince Dimitri of Yugoslavia and Prince Michael of Yugoslavia (1958–)
 * Prince Sergius of Yugoslavia and Princess Helene of Yugoslavia (1963–), younger siblings of Dimitri and Michael
 * Prince Jaime, Count of Bardi and Princess Margarita of Bourbon-Parma (1972–)
 * Prince Jean and Princess Margaretha of Luxembourg (1957–)
 * Prince Vincent and Princess Josephine of Denmark (2011–), fraternal twins of King Frederik X of Denmark and Queen Mary of Denmark
 * Shah Mohammad Reza Pahlavi (1919–1980) and Princess Ashraf Pahlavi of Iran (1919–2016)
 * Sempad (1276/1277–1310/1311) and Isabella of Armenia (1276/1277–1323)
 * Victoire de Valois (1556–1556) and Jeanne de Valois (died as an infant), twin daughters of Henry II of France and Catherine de Medici
 * Princess Amalie (1776–1823) and Caroline of Baden (1776–1841), Caroline was mother of two sets of twins: Elizabeth and Amalie; Sophie and Maria
 * Elisabeth Ludovika of Bavaria (1801–1873) and Princess Amalie Auguste of Bavaria (1801–1877), older sisters to Sophie and Maria; older twin daughters of Caroline
 * Princess Sophie of Bavaria (1805–1872) and Princess Maria Anna of Bavaria (1805–1877), younger sisters to Elizabeth and Amalie; younger twin daughters of Caroline
 * Umberto of Vidin (1999–) and Sofia of Vidin (1999–), twins of Prince Konstantin-Assen of Vidin, Prince of Bulgaria and María García de la Rasilla y Gortázar.
 * Princess Gabriella, Countess of Carladès and Jacques, Hereditary Prince of Monaco, (10 December 2014–), fraternal twins of Prince Albert II of Monaco and Princess Charlene of Monaco
 * Princess Henriette of Belgium (1870–1948) and Princess Joséphine Marie of Belgium (1870–1871)
 * Prince Nicolas and Prince Aymeric of Belgium (2005–), sons of Prince Laurent of Belgium and Princess Claire of Belgium
 * Princess Antonia and Prince Rupert of Prussia (1955–)
 * David II of Scotland (1324–1371) and John (1324–1327)
 * Archduchess Hermine of Austria (1817–1842) and Archduke Stephen of Austria (1817–1867)
 * Franz Wilhelm Prinz von Preussen (1943–) and Prince Friedrich Christian Ludwig of Prussia (1943)
 * Stephen II of Hungary (1101–1131) and Ladislaus
 * Prince Gabriel of Thurn and Taxis (1922–1942) and Princess Michaela of Thurn and Taxis (1922)
 * Princess Henriette Adelaide of Savoy (1636–1676) and Princess Catherine Beatrice of Savoy (1636–1637)
 * Maria Teresa of Savoy (1803–1879) and Maria Anna of Savoy (1803–1884)
 * Maria Cristina of Naples and Sicily (1779–1849) and Maria Cristina Amelia of Naples and Sicily (1779–1783)
 * Duchess Elsa of Württemberg (1876–1936) and Duchess Olga of Württemberg (1876–1932)

Scientists

 * Eric and Ian Agol (1970–)
 * Alex and Michael Bronstein (1980–)
 * Brian and Keith Conrad (1970–)
 * Frank and John Craighead (1916–2001 & 2016)
 * Mark and Scott Kelly (1964–)
 * Maurice Hilleman (1919–2005)
 * Stewart and Cyril Marcus (1930–1975)
 * Oleg and Igor Minin (1960– )
 * Riazuddin (1930–2013) and Fayyazuddin (1930–)
 * Erik and Herman Verlinde (1962–)
 * Alexei (1952–2007) and Alexander Zamolodchikov (1952–)
 * Sun Zhiwei and Sun Zhihong (1965–)
 * Henryk and Tadeusz Iwaniec (1947–)
 * Akiva and Isaak Yaglom (1921–2007 & 1988)
 * Xand and Chris van Tulleken (1978–)

Sportspeople

 * Stanislav and Yaroslav Alshevsky (1991–)
 * Dan and Ran Alterman (1980–)
 * Hamit and Halil Altıntop (1982–)
 * Mario (1940–) and Aldo Andretti (1940–2020)
 * Archil and Shota Arveladze (1973–)
 * Arina Averina and Dina Averina (1998–)
 * McWilliams and McJoe Arroyo (1985–)
 * Herbert (1872–1931) and Wilfred Baddeley (1872–1929)
 * Ronde and Tiki Barber (1975–)
 * Bob and Dave Barney (1932–)
 * Patrick and Pascal Barré (1959–)
 * Guillermo and Gustavo Barros Schelotto (1973–)
 * Alec (1918–2010) and Eric Bedser (1918–2006)
 * Brie and Nikki Bella, aka The Bella Twins (1983–)
 * Lars and Sven Bender (1989–)
 * Vasili and Aleksei Berezutski (1982–)
 * Mikhail and Vladimir Beschastnykh (1974–)
 * Nicholas Bett (1990–2018) and Aron Koech (1990–)
 * Bernadett and Ilona Biacsi (1985–)
 * Alex and Kate Blackwell (1983–)
 * Hannah and Holly Blossom (1988–), real names Lucy and Kelly Knott
 * Frank and Ronald de Boer (1970–)
 * Kevin and Jonathan Borlée (1988–)
 * Tom and Terry Brands (1968–)
 * Bob and Mike Bryan (1978–); see also Bryan brothers, their tennis doubles partnership
 * Josh and Daniel Bullocks (1983–)
 * Heather and Heidi Burge (1971–)
 * George Burgess and Thomas Burgess (1992–)
 * Chris and Nicky Cadden (1996–)
 * Jim and Finlay Calder (1957–)
 * José Maria and Juan Miguel "Juanmi" Callejón (1987–)
 * Dick and Ian Campbell (1953–)
 * Jose and Ozzie Canseco (1964–)
 * Dionísio and Domingos Castro (1963–)
 * Pierre and Pablo Caesar (1980–)
 * Adam and James Chambers (1980–)
 * David and Malcolm Changleng (1970–)
 * Jermall and Jermell Charlo (1990–), American boxers
 * Giulio and Nicola Ciotti (1976–)
 * Jarron and Jason Collins (1978–)
 * Felipe and Manuel Contepomi (1977–)
 * Angela and Amber Cope (1983–)
 * Tim and Tom Coronel (1972–)
 * Cui Qi and Cui Lin (1997–)
 * Alice and Asia D'Amato (2003–)
 * Paul Dawson and Chris Dawson (rugby league) (1948–)
 * Philipp and David Degen (1983–)
 * Isabelle and Véronique Delobel (1978–)
 * Jorge and Julio Dely Valdés (1967–)
 * Christoph and Markus Dieckmann (1976–)
 * Mike and Ray DiMuro (1967–)
 * Lukáš and Tomáš Došek (1978–)
 * Jeroen and Henrico Drost (1987–)
 * James and Jason Dunn (1973–)
 * Jean-Luc du Preez and Dan du Preez (1995-)
 * Todd and Troy Dusosky (1976–)
 * Alexander and Vladimir Efimkin (1981–)
 * José and Vinicio Espinal (1982–)
 * Mark and J. Michael Evans (1957–)
 * Caroline and Georgina Evers-Swindell (1978–)
 * Anthony and Saia Fainga'a (1987–)
 * Jonathan and Joshua Fatu (1985–), professional wrestlers better known as Jimmy and Jey Uso.
 * Sam and Solofa Fatu (1965–), professional wrestlers; Solofa is better known as Rikishi. Solofa is also the father of the aforementioned Jonathan and Joshua Fatu.
 * Stephen and Matthew Febey (1969–)
 * Bia and Branca Feres (1988–)
 * Peter and Chris Ferraro (1973–)
 * Garrett and Brett Festerling (1986–)
 * Antonio and Emanuele Filippini (1973–)
 * Miguel and Javier Flaño (1984–)
 * Jörg and Uwe Freimuth (1961–)
 * Rogelio and Ramiro Funes Mori (1991–)
 * Ron Futcher and Paul Futcher (1956–)
 * Jennifer Gadirova and Jessica Gadirova (2004–)
 * Kaokor and Khaosai Galaxy (1959–)
 * Alexe Gilles and Piper Gilles (1992–)
 * Jack and Josh Goodhue (1995–)
 * Chris and James Gowans (1977–)
 * Joey and Stephen Graham (1982–)
 * Horace and Harvey Grant (1965–)
 * Suzanne and Shelley Grant (1984–)
 * Michael and Marcus Griffin (1985–)
 * Shaquem and Shaquill Griffin (1995–)
 * Adam and Joel Griffiths (1979–)
 * Ray (1893–1953) and Roy Grimes (1893–1954)
 * Emilio and Javi Guerra (1982–)
 * Tim (1951–1996) and Tom Gullikson (1951–)
 * Arnar and Bjarki Gunnlaugsson (1973–)
 * Paul and Morgan Hamm (1982–)
 * Harris Brothers (1961–)
 * Katrine Lunde Haraldsen and Kristine Lunde-Borgersen (1980–)
 * Aaron and Andrew Harrison (1994–)
 * Alvin and Calvin Harrison (1974–)
 * Hossam and Ibrahim Hassan (1966–)
 * Earl and Dave Hebner (1949–)
 * Richard and Michael Hills (1963–)
 * Pavol and Peter Hochschorner (1979–)
 * David and Dean Holdsworth (1968–)
 * Matt Hughes and Mark Hughes (1973–)
 * David (1937–) and Peter Jackson (1937–1991)
 * Duan Jansen and Marco Jansen (2000-)
 * Martin Johansen and Michael Johansen (1972–)
 * Sarah and Karen Josephson (1964–)
 * Dora and Larissa Kalaus (1996–)
 * Jenny and Susanna Kallur (1981–)
 * Michael and Will Keane (1993–)
 * René and Willy van de Kerkhof (1951–)
 * Gözde and Özge Kırdar (1985–)
 * Daniela (1982–2008) and Sandra Klemenschits (1982–)
 * Michael and Nigel Kol (1962–)
 * Erwin and Helmut Kremers (1949–)
 * Monique and Jocelyne Lamoureux (1989–)
 * Darjuš and Kšyštof Lavrinovič (1979–)
 * Li Guangwen and Li Shangwen (1992–)
 * Li Long and Li Qiang (1998–)
 * Liu Huan and Liu Le (1989–)
 * Lo Chih-an and Lo Chih-en (1988–)
 * Nathan and Ryan Lonie (1983–)
 * Brook and Robin Lopez (1988–)
 * Alistair and Stewart Lord (1940–)
 * Henrik and Joel Lundqvist (1982–)
 * Leona and Lisa Maguire (1994–)
 * Phil and Steve Mahre (1957–)
 * Hamish and James Marshall (1979–)
 * Caleb and Cody Martin (1995–)
 * Pat and Luke McCormack (1995–)
 * Devin and Jason McCourty (1987–)
 * Robby and Ross McCrorie (1998–)
 * Devon and Ricardo McDonald (1969–)
 * Jamie and Gavin McDonnell (1986–)
 * Marlin (1940–2006) and Mike McKeever (1940–1967)
 * Donnie and Ronnie McKinnon (1940–)
 * Eissa Meer and Ibrahim Meer (1967–)
 * Coco and Kelly Miller (1978–)
 * Ryan (1974–2023) and Damon Minor (1974–)
 * Jason and Andrew Moloney (1991–)
 * Kazuyuki and Kōji Morisaki (1981–)
 * Brett and Josh Morris (1987–)
 * Markieff and Marcus Morris (1989–)
 * Isabelle and Béatrice Mouthon (1966–)
 * Mildred and Marianne Muis (1968–)
 * Jacob and Josh Murphy (1995–)
 * Akona and Odwa Ndungane (1981–)
 * Phil Neville and Tracey Neville (1977–)
 * Antônio Rodrigo Nogueira and Antônio Rogério Nogueira (1976–), Brazil
 * Dennis and Gérard de Nooijer (1969–), Netherlands
 * Amanda and Isabelle Nylander (1990–), Sweden
 * Emilia and Erika Nyström (1983–), Finland
 * Federico and Salomón Obama (2000–), Equatorial Guinea
 * Kenji and Tsugiharu Ogiwara (1969–), Japan
 * Amanda and Tess Oliveira (1987–), Brazil
 * Hiromi and Takami Ominami (1975–), Japan
 * Edu and Joan Oriol (1986–)
 * Javier (1974–2018) and Ricardo Otxoa (1974–2001), Spain
 * Flávio and Marco Paixão (1984–)
 * Ashley and Courtney Paris (1987–)
 * Callum and Matt Parkinson (1996–)
 * Maksym (1988–2008) and Pavlo Pashayev (1988–)
 * Paula and María Paulina Pérez (1996–)
 * Elisabeth and Patricia Pinedo (1981–)
 * Mike and Dan Pletch (1983–)
 * Kristýna and Karolína Plíšková (1992–)
 * Jolanta and Rasa Polikevičiūtė (1970–)
 * Paula and Stela Posavec (1996–)
 * Mike and Maurkice Pouncey (1989–)
 * Andreas and Thomas Ravelli (1959–)
 * Ángel and Óscar Romero (1992–)
 * Rex and Rob Ryan (1962–)
 * Ebbe and Peter Sand (1972–)
 * Hisato and Yūto Satō (1982–)
 * Shu and Kei Sato (1977–)
 * Andy and Walt Schmetzer (1968–)
 * Chris and Brad Scott (1976–)
 * Daniel and Henrik Sedin (1980–)
 * Antonio and Piero Selvaggio (1958–)
 * Adam and Troy Selwood (1984–)
 * André and Anderson Silva (1997–)
 * Fábio and Rafael Pereira da Silva (1990–), Brazil

 * Shigeru and Takeshi So (1953–)
 * Pavel and Petr Štercl (1966–)
 * Sun Ji and Sun Xiang (1982–)
 * Patrik and Peter Sundström (1961–)
 * Ron and Rich Sutter (1963–)
 * Vladimir and Valeriy Sydorenko (1976–)
 * Tang Xin and Tang Miao (1990–)
 * Carl and Charles Thomas (1969–)
 * Tõnu and Toomas Tõniste (1967–)
 * Borislav and Radoslav Tsonev (1995–)
 * Karyne and Sarah Steben (1974–)
 * Mike and Todd Shane (1967–)
 * Dick and Tom Van Arsdale (1943–)
 * Mick and Tim van Dijke (2000–)
 * Jack and Jamie Vance (1997–)
 * Roel and Mansueto Velasco (1972–)
 * Peter and Martin Velits (1985–)
 * Romário and Ronaldo Vieira (1998–)
 * Chris and Patrick Vörös (1993–)
 * Zlatko and Zoran Vujović (1958–)
 * Darryl and Shane Wakelin (1974–)
 * Ray and Rod Wallace (1969–)
 * Kevin and Kerrod Walters (1967–)
 * Mark and Steve Waugh (1965–)
 * Elliot and Andrew Weber (1983–)
 * Dora and Cora Webber (1958–)
 * Alan and Gary Whetton (1959–)
 * Cameron and Tyler Winklevoss (1981–)
 * Yao Daogang and Yao Wei (1997–)
 * Adam and Simon Yates (1992–)
 * Cristian and Damiano Zenoni (1977–)
 * Marcin and Michał Żewłakow (1976–)
 * Bengt and Björn Zikarsky (1967–)
 * Taylor and Tyler Rogers (1990-)

Twins notable in each of their own separate fields

 * Paul and Andrea Boardman (1967–)
 * Jill and Jacqueline Hennessy (1968–)
 * Laverne Cox and M Lamar (1972–)
 * Rita (1909–2012) and Paola Levi-Montalcini (1909–2000)
 * Marcus and Morgan Luttrell (1975–)
 * Alexandra and Caroline Paul (1963–)
 * Charlotte and Samantha Ronson (1977–)
 * Carol and Mark Thatcher (1953–)
 * Gloria Morgan Vanderbilt (1904–1965) and Thelma Furness, Viscountess Furness (1904–1970)
 * David Gulpilil (1953–2021) and Mary Dhalapany (1953–)

Other

 * Barney M. Giles and Benjamin Franklin Giles, military officers
 * Johnny and Luther Htoo (c. 1988–), guerrilla leaders
 * Philip and Andrew Oliver (1968–), video game developers
 * Mary-Kate and Ashley Olsen (1986–), fashion designers
 * David and Peter Turnley, photojournalists
 * Poto and Cabengo (1970–), who invented a language to speak to each other

Conjoined twins

 * Carmen and Lupita Andrade (2000–)
 * Ladan and Laleh Bijani (1974–2003)
 * Chang and Eng Bunker (1811–1874), the original "Siamese twins"
 * Ronnie and Donnie Galyon (1951–2020), the world’s oldest conjoined twins to ever live.
 * Ilona and Judit Gófitz (1701–1723)
 * Abby and Brittany Hensel (born 1990)
 * Daisy and Violet Hilton (1908–1969)
 * Millie and Christine McKoy (1851–1912)
 * Radhika and Dudhika Nayak (born 1888; Dudhika died in 1902, Radhika in 1903)
 * Spider Girls, Ganga and Jamuna Mondal (born Ayara and Jayara Ratun in 1969 or 1970)

Notable people with a non-famous twin

 * Brooke Adams, fraternal twin sister
 * James Alexandrou, twin sister
 * Chad Allen, twin sister
 * Stephen K. Amos, twin sister
 * Carl Anderson, twin brother died as an infant
 * Kofi Annan, twin sister
 * Richie Ashburn, twin sister
 * Lillian Asplund, twin brother
 * Gracia Baur, twin sister
 * Marc Bartra, twin brother
 * Albert Belle, twin brother
 * Blaze Berdahl, twin sister
 * Josh Bernstein, twin brother
 * Jonathon Blum, twin sister died in a house fire in 2004
 * Eugenie Bouchard, fraternal twin sister
 * Crystal Bowersox, fraternal twin brother
 * Nicholas Brendon, twin brother
 * Bob Brown, twin sister
 * Gisele Bündchen, fraternal twin sister
 * Aaron Carter, twin sister
 * Gabrielle Carteris, twin brother
 * Candis Cayne, fraternal twin brother
 * Karen Cellini, twin sister
 * Justin Chambers, twin brother
 * Keith Chegwin, twin brother
 * Gary Cherone, fraternal twin brother
 * Montgomery Clift, twin sister
 * Carlo Colaiacovo, brother
 * Henry Cooper, twin brother
 * Bucky Covington, twin brother
 * Curley Culp, twin sister
 * Andrew Daddo, fraternal twin
 * Ann B. Davis, twin sister
 * Anthony Davis, twin sister
 * Cody Deal, twin brother
 * Fennis Dembo, twin sister
 * Philip K. Dick, twin sister died after birth
 * Vin Diesel, fraternal twin brother
 * Nyle DiMarco, fraternal twin brother
 * Jamie Dimon, fraternal twin brother
 * Duffy, twin sister
 * Alain Eizmendi, identical twin brother
 * Marc Elliott, twin sister
 * Karen Elson, fraternal twin sister
 * John Elway, twin sister
 * Theo Epstein, twin brother
 * Mike Espy, twin sister
 * Jerry Falwell, twin brother
 * Joseph Fiennes, twin brother
 * Caroline Flack, twin sister
 * John "Ecstasy" Fletcher (of Whodini), twin brother
 * Adam Foote, twin sister
 * Samantha Futerman, identical twin sister raised separately as a citizen of France
 * Max Gail, twin sister
 * Lucía García, twin brothers
 * Dave Gorman, twin brother
 * Noah Gragson, twin sister
 * Eva Green, fraternal twin sister
 * Jerry Hall, twin sister
 * Linda Hamilton, twin sister
 * Victor Davis Hanson, fraternal twin brother
 * Ella Harper, unnamed twin brother died shortly after birth
 * Gordon Hayward, twin sister
 * Jon Heder, identical twin brother
 * William Randolph Hearst, twin died as an infant
 * Marilu Henner, twin sister
 * John Hensley, fraternal twin sister
 * Alex Hirsch, twin sister
 * Ryan Howard, twin brother
 * Sabrina Ionescu, twin brother
 * Urtzi Iriondo, identical twin brother
 * Carlin Isles, twin sister
 * Marlon Jackson, twin brother died at birth
 * David Jason, twin brother died during birth
 * Chris Joannou, twin sister
 * Scarlett Johansson, twin brother
 * Siva Kaneswaran, twin brother
 * Jay Kay, twin brother died at birth
 * Tom Kean Jr., twin brother
 * Cory Kennedy, fraternal twin sister
 * Joseph P. Kennedy III, fraternal twin brother
 * Junsu Kim, fraternal twin brother
 * David Kohan, twin brother
 * Ashton Kutcher, fraternal twin brother
 * Gabriel Landeskog, twin sister
 * Chris Lane, twin brother
 * Kate Lawler, twin sister
 * Gigi Leung, twin brother
 * Liberace, twin died as an infant
 * Tony Liberatore, twin brother
 * Cory Lidle, twin brother
 * Jon Lindsay, fraternal twin brother
 * Thad Luckinbill, twin brother
 * Tom Luginbill, twin sister
 * John Maine, fraternal twin brother
 * Rami Malek, identical twin brother
 * Shawn Marion, twin sister
 * Susie Maroney, fraternal twin
 * Logan Marshall-Green, twin brother
 * Roberta McCain, twin sister
 * Paul McDermott
 * Jay McGuiness, identical twin brother
 * Gene McKinney, twin brother
 * Victor A. McKusick, twin brother
 * Alanis Morissette, twin brother
 * Alma Miettinen, twin sister
 * Burt Munro, twin sister died at birth
 * Olly Murs, fraternal twin brother
 * Mandy Musgrave, identical twin sister
 * Maye Musk, identical twin sister
 * Gaute Ormåsen, fraternal twin brother
 * Jason Orange, twin brother
 * John Osborne, twin sister
 * Melanie Oudin, twin sister
 * Autumn Phillips, twin brother
 * Parker Posey, twin brother
 * Elvis Presley, twin brother died at birth
 * Richard Quest, twin sister
 * Megan Rapinoe, twin sister
 * Dack Rambo, twin brother
 * Efren Ramirez, identical twin brother
 * Judy Reyes, twin sister
 * Pekka Rinne, twin sister
 * Marty Robbins, twin sister
 * Isabella Rossellini, twin sister
 * J. D. Roth, twin sister
 * Stark Sands, fraternal twin brother
 * Gorka Santamaría, identical twin brother
 * Brian Schatz, twin brother
 * Noah Schnapp, twin sister
 * Judith Scott, twin sister
 * Teemu Selänne, twin brother
 * Sab Shimono
 * Bill Shorten, twin brother
 * Lori Singer, twin brother
 * Tasha Smith, twin sister
 * Katy Steele, twin brother
 * Curtis Strange, twin brother
 * Ed Sullivan, twin brother died as an infant
 * Sandra Sully
 * Charles Sumner, twin sister
 * Kiefer Sutherland, twin sister
 * Amanda Tapping, twin brother
 * Adam Thomas, fraternal twin brother
 * Jim Thome, twin sister
 * Jim Thorpe, twin brother
 * Frances Tiafoe, twin brother
 * Jon Tickle, twin brother
 * Garrett Tierney, identical twin brother
 * Paul Tsongas, twin sister
 * Ronan Tynan, twin brother died as an infant
 * Derek Thompson, twin sister
 * Sarah Vowell, twin sister
 * Emppu Vuorinen, twin brother
 * Wang Qiang, twin brother
 * Shayne Ward, twin sister
 * Ellen G. White, twin sister
 * Billy Dee Williams, twin sister
 * Ricky Williams, twin sister
 * Kane Williamson, twin brother
 * Marvin Winans, twin brother
 * Brad Womack, twin brother
 * Bang Yong Guk, twin brother

Twin records

 * Jane Haskin (1924-2001) and John Prosser Haskin, Jr. (1924-2004), Guinness World Records “World’s Heaviest Twins” with an aggregate weight of 12.58 kg (27 lbs 12 Oz), were born to Mary Ann Haskin (USA), of Fort Smith, Arkansas, USA on 20 February 1924.
 * Gin Kanie (1892–2001) and Kin Narita (1892–2000), widely known for their longevity
 * Benny (1947–2001) and Billy McGuire (1947–1979), heaviest ever twins at 814 and 784 pounds. Born in Hendersonville, NC, US in 1947. Billy died in 1979, Benny in 2001.
 * Michael and James Lanier, World's tallest twins, at 7' 6" or 2.286 m.
 * Edward and Daniel Hemberg (2005–), heaviest twins born in New Zealand (and at the time Australasia) via natural delivery (Edward 3.54 kg and Daniel 3.76 kg)
 * Tashi and Nungshi Malik (1991–), world's first female twins to scale Everest together, first twins and siblings to scale Seven Summits together, Ski to North & South Pole together and to complete Explorers Grand Slam together and youngest persons to achieve it
 * In 2017, at the age of 7, Ava Marie (2010–) and Leah Rose Clements (2010–) were recognized by multiple news outlets as the "world's most beautiful identical twins."

title: List of twins


text:
Line bundle

In mathematics, a line bundle expresses the concept of a line that varies from point to point of a space. For example, a curve in the plane having a tangent line at each point determines a varying line: the tangent bundle is a way of organising these. More formally, in algebraic topology and differential topology, a line bundle is defined as a vector bundle of rank 1.

Line bundles are specified by choosing a one-dimensional vector space for each point of the space in a continuous manner. In topological applications, this vector space is usually real or complex. The two cases display fundamentally different behavior because of the different topological properties of real and complex vector spaces: If the origin is removed from the real line, then the result is the set of 1×1 invertible real matrices, which is homotopy-equivalent to a discrete two-point space by contracting the positive and negative reals each to a point; whereas removing the origin from the complex plane yields the 1×1 invertible complex matrices, which have the homotopy type of a circle.

From the perspective of homotopy theory, a real line bundle therefore behaves much the same as a fiber bundle with a two-point fiber, that is, like a double cover. A special case of this is the orientable double cover of a differentiable manifold, where the corresponding line bundle is the determinant bundle of the tangent bundle (see below). The Möbius strip corresponds to a double cover of the circle (the θ → 2θ mapping) and by changing the fiber, can also be viewed as having a two-point fiber, the unit interval as a fiber, or the real line.

Complex line bundles are closely related to circle bundles. There are some celebrated ones, for example the Hopf fibrations of spheres to spheres.

In algebraic geometry, an invertible sheaf (i.e., locally free sheaf of rank one) is often called a line bundle.

Every line bundle arises from a divisor with the following conditions

(I) If X is reduced and irreducible scheme, then every line bundle comes from a divisor.

(II) If X is projective scheme then the same statement holds.

The tautological bundle on projective space
One of the most important line bundles in algebraic geometry is the tautological line bundle on projective space. The projectivization P(V) of a vector space V over a field k is defined to be the quotient of $$V \setminus \{0\}$$ by the action of the multiplicative group k×. Each point of P(V) therefore corresponds to a copy of k×, and these copies of k× can be assembled into a k×-bundle over P(V). k× differs from k only by a single point, and by adjoining that point to each fiber, we get a line bundle on P(V). This line bundle is called the tautological line bundle. This line bundle is sometimes denoted $$\mathcal{O}(-1)$$ since it corresponds to the dual of the Serre twisting sheaf $$\mathcal{O}(1)$$.

Maps to projective space
Suppose that X is a space and that L is a line bundle on X. A global section of L is a function s : X → L such that if p : L → X is the natural projection, then ps= idX. In a small neighborhood U in X in which L is trivial, the total space of the line bundle is the product of U and the underlying field k, and the section s restricts to a function U → k. However, the values of s depend on the choice of trivialization, and so they are determined only up to multiplication by a nowhere-vanishing function.

Global sections determine maps to projective spaces in the following way: Choosing r + 1 not all zero points in a fiber of L chooses a fiber of the tautological line bundle on Pr, so choosing r + 1 non-simultaneously vanishing global sections of L determines a map from X into projective space Pr. This map sends the fibers of L to the fibers of the dual of the tautological bundle. More specifically, suppose that s0, ..., sr are global sections of L. In a small neighborhood U in X, these sections determine k-valued functions on U whose values depend on the choice of trivialization. However, they are determined up to simultaneous multiplication by a non-zero function, so their ratios are well-defined. That is, over a point x, the values s0(x), ..., sr(x) are not well-defined because a change in trivialization will multiply them each by a non-zero constant λ. But it will multiply them by the same constant λ, so the homogeneous coordinates [s0(x) : ... : sr(x)] are well-defined as long as the sections s0, ..., sr do not simultaneously vanish at x. Therefore, if the sections never simultaneously vanish, they determine a form [s0 : ... : sr] which gives a map from X to Pr, and the pullback of the dual of the tautological bundle under this map is L. In this way, projective space acquires a universal property.

The universal way to determine a map to projective space is to map to the projectivization of the vector space of all sections of L. In the topological case, there is a non-vanishing section at every point which can be constructed using a bump function which vanishes outside a small neighborhood of the point. Because of this, the resulting map is defined everywhere. However, the codomain is usually far, far too big to be useful. The opposite is true in the algebraic and holomorphic settings. Here the space of global sections is often finite dimensional, but there may not be any non-vanishing global sections at a given point. (As in the case when this procedure constructs a Lefschetz pencil.) In fact, it is possible for a bundle to have no non-zero global sections at all; this is the case for the tautological line bundle. When the line bundle is sufficiently ample this construction verifies the Kodaira embedding theorem.

Determinant bundles
In general if V is a vector bundle on a space X, with constant fibre dimension n, the n-th exterior power of V taken fibre-by-fibre is a line bundle, called the determinant line bundle. This construction is in particular applied to the cotangent bundle of a smooth manifold. The resulting determinant bundle is responsible for the phenomenon of tensor densities, in the sense that for an orientable manifold it has a nonvanishing global section, and its tensor powers with any real exponent may be defined and used to 'twist' any vector bundle by tensor product.

The same construction (taking the top exterior power) applies to a finitely generated projective module M over a Noetherian domain and the resulting invertible module is called the determinant module of M.

Characteristic classes, universal bundles and classifying spaces
The first Stiefel–Whitney class classifies smooth real line bundles; in particular, the collection of (equivalence classes of) real line bundles are in correspondence with elements of the first cohomology with Z/2Z coefficients; this correspondence is in fact an isomorphism of abelian groups (the group operations being tensor product of line bundles and the usual addition on cohomology). Analogously, the first Chern class classifies smooth complex line bundles on a space, and the group of line bundles is isomorphic to the second cohomology class with integer coefficients. However, bundles can have equivalent smooth structures (and thus the same first Chern class) but different holomorphic structures. The Chern class statements are easily proven using the exponential sequence of sheaves on the manifold.

One can more generally view the classification problem from a homotopy-theoretic point of view. There is a universal bundle for real line bundles, and a universal bundle for complex line bundles. According to general theory about classifying spaces, the heuristic is to look for contractible spaces on which there are group actions of the respective groups C2 and S1, that are free actions. Those spaces can serve as the universal principal bundles, and the quotients for the actions as the classifying spaces BG. In these cases we can find those explicitly, in the infinite-dimensional analogues of real and complex projective space.

Therefore the classifying space BC2 is of the homotopy type of RP∞, the real projective space given by an infinite sequence of homogeneous coordinates. It carries the universal real line bundle; in terms of homotopy theory that means that any real line bundle L on a CW complex X determines a classifying map from X to RP∞, making L a bundle isomorphic to the pullback of the universal bundle. This classifying map can be used to define the Stiefel-Whitney class of L, in the first cohomology of X with Z/2Z coefficients, from a standard class on RP∞.

In an analogous way, the complex projective space CP∞ carries a universal complex line bundle. In this case classifying maps give rise to the first Chern class of X, in H2(X) (integral cohomology).

There is a further, analogous theory with quaternionic (real dimension four) line bundles. This gives rise to one of the Pontryagin classes, in real four-dimensional cohomology.

In this way foundational cases for the theory of characteristic classes depend only on line bundles. According to a general splitting principle this can determine the rest of the theory (if not explicitly).

There are theories of holomorphic line bundles on complex manifolds, and invertible sheaves in algebraic geometry, that work out a line bundle theory in those areas.

title: Line bundle