Marrying with relatives isn’t a new thing for any royal family in the world. Hapsburgs generally come to mind, but Windsors aren’t strangers to the practice either, even in modern times. Queen Elizabeth II and Prince Philip, Prince William and Kate Middleton, even Prince Harry and Meghan Markle are related to each other.
Prince Andrew and his ex-wife, Sarah Ferguson are also distant cousins, but not only that, they have family ties across Atlantic as well, just like the late Princess Diana, Princess of Wales.
Both Diana and Sarah are descendants of William Cavendish, which makes them fourth cousins. They were close in their younger years, but had a falling out in 1996 and never got a chance to mend things up before Diana died in a tragic car accident in Paris.
Diana is related to the Bush family. Her and the 43rd president of the United States, George W. Bush were 11th cousins, twice removed. The families kept in touch and visited each other. The Bushes are also related to Abraham Lincoln and Marylin Monroe.
Sarah Ferguson, on the other hand, is related to the sixth President of the United States, John Quincy Adams. She is his seventh cousin, seven times removed. She is also related to John Winthrop, who founded the Massachusetts Bay Colony.
Some other people you wouldn’t expect are also related to the royal family. Ellen DeGeneres is 15th cousin with Kate Middleton, while Camilla Parker Bowles is Madonna’s 9th cousin.
Michael Douglas and Beyoncé are related to Queen Elisabeth, through King Edward III and Henry II respectively, but the closest relative Queen has across the pond is Hilary Duff. Their joint ancestor Henry III makes them 18th cousins.
Source: cheatsheet.com