Cousin Relationships of British Monarchs and Consorts

1840: Queen Victoria's marriage to her first cousin had virtually no strategic or economic advantage, and was purely based on the attraction between the couple and the desire of Victoria to break out the strict and elaborate set of rules designed by her mother concerning her upbringing. This marriage produced 9 children, and 40 grandchildren and over 1000 total descendants that constitute a sizable portion of the royalty in Europe over the last century and a half. The deadly genetic disease, hemophilia, which started with Victoria is unrelated to the first cousin marriage.

• Of the four first-cousin marriages (no times removed), only the marriage of George I and Sophia Dorothea of Celle was a parallel cousin marriage. The fathers of the couple,George William, Duke of Brunswick-Lüneburg and Ernest Augustus, Elector of Brunswick-Lüneburg were brothers. Both brothers were alive when George imprisoned his ex-wife. The other three royal cousin marriages were of cross cousins, where the parents who were siblings were brother and sister.

• The most recent common ancestor of George VI of the United Kingdom and his wife Elizabeth Bowes-Lyon was Henry VII who had died over 400 years before their marriage. When the future king married his 13th cousin on 26 April 1923 his older brother, Edward VIII, the heir apparent was still only age 28 and was still expected to marry and succeed to the throne. However, shortly after the marriage, Edward began to openly talk about his desire to abdicate and make his brother the sovereign, which he actually did 13 years later. This marriage was the most distant family relationship that produced a child that also became a sovereign. It was also the first time since James II that a sovereign married a spouse of primarily British descent. It was also the first time since Henry VIII that a sovereign married someone who was more distantly related than 3rd cousin once removed (not including Edward VIII, marrying Wallis Simpson after his abdication).

• The most recent common ancestor of Elizabeth II and her husband Prince Philip was Christian IX of Denmark who had died in 1906. The table list the closest familial relationship, but sometimes more distant relationships are better known. Queen Elizabeth II, and her consort, Prince Philip are also 3rd cousins from their descent from Queen Victoria who died in 1901. Both the marriage of Princess Elizabeth to Prince Philip and the potential arrangements to marry Prince Charles to Amanda Knatchbull were primarily the result of the matchmaking skills of Louis Mountbatten, 1st Earl Mountbatten of Burma. He was the uncle to Prince Phillip and the grandfather to Amanda Knatchbull. His [...] by an IRA bomb in 1979, which also killed another grandmother of Amanda as well as her younger brother caused her to recoil at the prospect of marrying into the royal family. She refused Charles subsequent proposal and he married his much more distant relative Diana.

• Charles and Diana's most recent common ancestor was William Cavendish, 3rd Duke of Devonshire and his wife, who died in the last half of the 18th century. Since they both had well documented pedigrees, they have hundreds of known ancestors in common before that time.

• Charles and Camilla's most recent common ancestor is James I who died in 1625.

• Kate Middleton may be a descendant of Mary Boleyn via her daughter, Catherine Carey. Kate Middleton’s 7Xgreat-grandfather William Davenport (d. 1723) may be a son born in 1679 to Henry Davenport of Hollon. If this relationship probes accurate (DNA confirmation may be required)then Kate is descended from Mary Boleyn. Prince William of Wales is also descended from Mary Boleyn via both her son Henry Carey, 1st Baron Hunsdon and her daughter. Both of Mary Boleyn's children are rumored to be the illegitimate children of Henry VIII.

• Prince Arthur of Connaught was a first cousin to George V. He married his first cousin once removed, Princess Alexandra, Duchess of Fife on 15 October 1913, and the couple had a son, Alistair, 9.8 months later. Alistair was born 9th in line to the throne and died 12th in line in 1943. He is the last child born to a couple consisting of first cousins once removed in the British royal family.