Famous cousins

Braulio Álvarez Castillo, Dominican Republic military man, and his double cousin, María Álvarez Guerra

Josiah Bartlett, second signer of the United States Declaration of Independence, and his first cousin, Mary Bartlett

Christine Boutin, French politician, and her first cousin, Louis Boutin

Wernher von Braun, German-American aerospace engineer, and his first cousin, Maria Luise von Quistorp

Charles Bulfinch, American architect, and his first cousin, Hannah Apthorp

Charles Darwin and his first cousin, Emma Wedgwood.  In addition, their grandparents, Sarah Wedgwood and Josiah Wedgwood, were third cousins.

Andrew Jackson Donelson, American diplomat, and his cousins Emily Donelson and Elizabeth Martin Randolph

Albert Einstein and his first cousin (through his mother) and second cousin (through his father), Elsa Löwenthal née Einstein

William Greenleaf Eliot, founder of Washington University in St. Louis (and grandfather of poet T. S. Eliot), married his first cousin once removed but more notable is that his father, mother, and wife were first cousins of each other.

William Crowninshield Endicott, former US Secretary of War, and his first cousin, Ellen Peabody

Ulises Espaillat, Dominican Republic president, and his first cousin, Eloísa Espaillat

Vivian Fuchs, British explorer, and his cousin Joyce Connell

Viriato Fiallo, Dominican Republic politician, and his first cousin, Prudencia Fiallo

Carlo Gambino, a mob boss, and his first cousin, Catherine Castellano

André Gide, Nobel Prize-winning French author, and his cousin, Madeleine Rondeaux

Charlotte Perkins Gilman, American author, and her first cousin, George Houghton Gilman

Carl Giles, cartoonist, and his cousin Joan Giles

Laurent Gouvion, French general and later Marshal of the Empire, and his first cousin, Anne Gouvion

Edvard Grieg, Norwegian composer, and his first cousin, Nina Hagerup

Alexander Herzen, Russian writer and political activist, and his cousin, Natalya Zakharina

Saddam Hussein and his first cousin Sajida Talfah

Jesse James and his first cousin, Zerelda "Zee" Mimms

Jón Sigurðsson, leader of the 19th-century Icelandic independence movement, and his first cousin, Ingibjörg Einarsdóttir

Naoto Kan, former Prime Minister of Japan, and his first cousin, Nobuko

Nobusuke Kishi, former Japanese statesman, and his first cousin, Yoshiko Kishi

David Lean, British film director, and his first cousin, Isabel Lean

John A. Macdonald, first prime minister of Canada, and his first cousin, Isabella Clark

Rob Roy MacGregor, Scottish outlaw and folk hero, and his cousin Mary Helen MacGregor of Comar

Gerardo Machado y Morales, fifth president of Cuba, and his first cousin, Elvira Machado Nodal

Maeda Toshiie, Japanese Daimyō in the 15th century, and his cousin, Matsu

Mohammed bin Rashid Al Maktoum, Prime Minister of the United Arab Emirates, and his first cousin, Hind bint Maktoum bin Juma Al Maktoum

Delarivier Manley, British playwright and political satirist, and her first cousin John Manley

Francis Marion, American revolutionary leader also called the "Swamp Fox," and his first cousin, Mary Esther Videau

Abraham Maslow, father of humanistic psychology, and his first cousin, Bertha Goodman

Matthew Fontaine Maury and his first cousin, Ann Hull Herndon

Darius Milhaud, French composer, and his first cousin, Madeleine Milhaud

Christopher Robin Milne, son of author A. A. Milne and the Christopher Robin of the Winnie-the-Pooh books, and his first cousin Lesley Sélincourt

Marina Mora, Peruvian beauty queen and former Miss Peru, and her first cousin Gustavo Mora

Mōri Terumoto, Japanese Daimyo in late 15th and early 16th century, and his cousin and first wife, Minami no Kata

Ignacy Mościcki, Polish chemist and president and his first cousin, Michalina Czyżewska

Muhammad and his first cousin, Zaynab bint Jahsh

Naoe Kanetsugu, Japanese samurai and Karō of the Uesugi clan in 15th and 16th century, and his cousin, Osen

Ōtomo no Yakamochi, Japanese statesman and waka poet in the Nara period, and his cousin, Sakanoue no Ōiratsume

Edgar Allan Poe, 27, and his first cousin, Virginia Clemm, 13

Bolesław Prus, Polish novelist, and his cousin, Oktawia Trembińska

Sergei Rachmaninoff, composer, and his cousin, Natalia Satina

Satyajit Ray, Indian film-maker, and his first cousin, Bijoya Ray

Eisaku Sato, prime minister of Japan, and his cousin, Hiroko Sato

Greta Scacchi, actress of Presumed Innocent, and her first cousin, Carlo Mantegazza

Igor Stravinsky, composer, and his first cousin, Katerina Nossenko

Toyotomi Hideyori, Japanese Daimyō, and his cousin, Senhime

Mario Vargas Llosa, Peruvian writer and 2010 Nobel Prize laureate, and his first cousin Patricia Llosa

H. G. Wells, author, and his first cousin and first wife Isabel Mary Wells

William Whipple, signer of the Declaration of Independence, and his first cousin, Catherine Moffatt

Afonso V of Portugal and his first cousin Isabel of Coimbra

Alfonso XI of Castile and his double first cousin and second wife Maria of Portugal

Alfonso XII of Spain and his first cousin and first wife Mercedes of Orleans

Grand Duchess Catherine Pavlovna of Russia and her first cousin and first husband Duke George of Oldenburg and her first cousin and second husband William I of Wurttemberg

Charles the Bold, Duke of Burgundy and his first cousin and second wife Isabella of Bourbon

Charles IV of Spain and his first cousin Maria Luisa of Parma

Charles V, Holy Roman Emperor and his first cousin Isabella of Portugal

Christian VII of Denmark and his first cousin Princess Caroline Matilda of Wales

Christian VIII of Denmark and his first cousin Duchess Charlotte Frederica of Mecklenburg-Schwerin

Drusus Julius Caesar and his first cousin Livilla

Archduchess Elisabeth Franziska of Austria and her first cousin and second husband Archduke Karl Ferdinand of Austria

Ernest Augustus I of Hanover and his first cousin Frederica of Mecklenburg-Strelitz

Ferdinand III, Grand Duke of Tuscany and his double first cousin Princess Luisa of Naples and Sicily

Francis I of the Two Sicilies and his double first cousin and first wife Archduchess Maria Clementina of Austria and first cousin and second wife Maria Isabella of Spain

Francis II, Holy Roman Emperor and his double first cousin and second wife Princess Maria Theresa of Naples and Sicily and his first cousin Archduchess Maria Ludovika of Austria-Este

Franz Joseph I of Austria and his first cousin Duchess Elisabeth in Bavaria

Frederick VI of Denmark and his first cousin Princess Marie Sophie of Hesse-Kassel

Frederick William I of Prussia and his first cousin Princess Sophia Dorothea of Hanover

Frederick William II of Prussia and his double first cousin Elisabeth Christine of Brunswick-Wolfenbuttel

George I of Great Britain and his first cousin Duchess Sophia Dorothea of Brunswick-Celle

George IV of the United Kingdom and his first cousin Princess Caroline of Brunswick-Wolfenbuttel

Gian Galeazzo Visconti, Duke of Milan and his first cousin Caterina Visconti

Haakon VII of Norway and his first cousin Princess Maud of Wales

Princess Henrietta Anne of England and her first cousin Philippe I, Duke of Orleans

Princess Irene of Hesse and by Rhine and her first cousin Prince Henry of Prussia

Isabella II of Spain and her double first cousin Francis, Duke of Cadiz

John Manuel, Prince of Portugal and his double first cousin Archduchess Joan of Austria

John II of Portugal and his first cousin Eleanor of Viseu

John III of Portugal and his first cousin Catherine of Austria

John V of Portugal and his first cousin Maria Anna of Austria

Julia and her first cousin and first husband Nero Caesar

Julia the Elder and her first cousin Marcus Claudius Marcellus

Karl Anton August, Prince of Schleswig-Holstein-Sonderburg-Beck and his first cousin Countess Charlotte of Dohna-Schlodien

Khalil of Bithynia and his first cousin Irene Palaiologina

Leopold I, Holy Roman Emperor and his first cousin and first wife Margarita Teresa of Spain

Leopold II, Grand Duke of Tuscany and his first cousin and second wife Princess Maria Antonia of the Two Sicilies

Louis II, Grand Duke of Hesse and his first cousin Princess Wilhelmine of Baden

Louis XIV of France and his double first cousin Maria Theresa of Spain

Princess Marie Therese of France and her first cousin Louis Antoine, Duke of Angouleme

Maximilian II, Holy Roman Emperor and his first cousin Maria of Spain

Miguel, Duke of Braganza and his first cousin Princess Maria Theresa of Lowenstein-Wertheim-Rosenberg

Napoleon Louis Bonaparte and his first cousin Charlotte Napolene Bonaparte

Olav V of Norway and his first cousin Princess Martha of Sweden

Philip II of Spain and his double first cousin Maria Manuela, Princess of Portugal

Charlotte, Grand Duchess of Luxembourg and her first cousin Prince Felix of Bourbon-Parma

Prince Philippe, Count of Paris and his first cousin Princess Marie Isabelle of Orleans

Umberto I of Italy and his first cousin Princess Margherita of Savoy

Victor Emmanuel II of Italy and his first cousin Archduchess Adelaide of Austria

Princess Victoria Melita of Saxe-Coburg and Gotha and her first cousin and first husband Ernest Louis, Grand Duke of Hesse and by Rhine and her first cousin and second husband Grand Duke Cyril Vladimirovich of Russia

Queen Victoria of the United Kingdom and her first cousin Prince Albert of Saxe-Coburg and Gotha

Prince William Frederick, Duke of Gloucester and Edinburgh and his first cousin Princess Mary of Great Britain

William I of the Netherlands and his first cousin Princess Wilhelmine of Prussia

William III of the Netherlands and his first cousin and first wife Princess Sophie of Wurttemberg

William III of England and his first cousin Mary II of England

Wladyslaw IV, king of Poland and his first cousin and first wife Cecilia Renata of Austria

Airlangga, regional king of Bali, Indonesia and his first cousin

Emperor Ichijō of Japan and his wife Fujiwara no Akiko

Emperor Kōbun of Japan and Empress Tōchi

Prince Nagaya of Japan and his wife Princess Kibi

Prince Shōtoku of Japan and his wife Princess Uji no Kaitako

Zaitian, the Guangxu Emperor and his first cousin, Yehenara Jingfen

Vajiralongkorn, Crown Prince of Thailand and his first cousin Mom Luang Soamsavali Kitiyakara

Emperor Zhongzong of Tang and his first cousin Lady Zhao

Emperor Wen of Western Wei and his first cousin Lady Yifu

Emperor Wu of Han and his first cousin Chen Jiao

Princess Baling of Tang (daughter of Emperor Taizong of Tang) and her first cousin Chai Lingwu, Duke of Xiangyang

Princess Taiping of Tang and her first husband and first cousin Xue Shao

Li Xianhui, Lady Yongtai and her first cousin Wu Yanji, Prince of Wei

Li Guo'er, Princess Anle and her second husband and first cousin Wu Yanxiu, Prince of Huaiyang

King Xerxes I of Persia and his first cousin Amestris

King Antiochus III the Great of the Seleucid Empire and his first cousin Princess Laodice of Pontus

King Mithridates III of Commagene and his first cousin Princess Isias Philostorgos of Cappadocia

Antiochus VIII Grypus of the Seleucid Empire and his first cousin Princess Tryphaena of Egypt

Pedro Sánchez de Tagle, 2nd Marquis of Altamira and his first cousin Luisa Sánchez de Tagle

María de la Paz Rodríguez Albuerne y Girón and her first cousin José María Trespalacios Rodríguez de Albuerne

Lord Edward Cavendish and his first cousin Emma Lascelles

Henry Sturt, 1st Baron Alington and his first cousin and first wife Lady Augusta Bingham

George Spencer-Churchill, 6th Duke of Marlborough and his first cousin and first wife Lady Jane Stewart

Double first cousins share both sets of grandparents and have twice the degree of consanguinity of ordinary first cousins; genetically they are as related as half-siblings.  If a pair of identical twins married another pair of identical twins, their children would be considered double cousins but genetically they would be the equivalent to full siblings.