Barack Obama often jokes in his campaign speeches about a genealogical survey last year that found he is a distant cousin of Dick Cheney.

Researchers at the New England Historic Genealogical Society, founded in 1845, said Obama, the son of a white woman from Kansas and a black man from Kenya, can call six US presidents his cousins: both Bushes, Gerald Ford, Lyndon Johnson, Harry Truman and James Madison. The society, a non-profit organisation, found he is also related to Churchill.

It said it investigated the blood lines of the three presidential hopefuls. One of the oddest connections is that Obama is related to Brad Pitt and Hillary Clinton to Pitt's partner, Angelina Jolie.