Clinton, who is of French-Canadian descent on her mother's side, is also a distant cousin of singers Madonna, Celine Dion and Alanis Morissette. Obama, the son of a white woman from Kansas and a black man from Kenya, can call six U.S. presidents, including George W. Bush, his cousins. McCain is a sixth cousin of first lady Laura Bush.
"You'd think with all that singing talent in the family she'd be able to carry a tune," Clinton's senior adviser Philippe Reines said. "But now it makes much more sense how she snagged a Grammy."
Clinton won for best spoken word Grammy in 1997 for "It Takes a Village." Obama also won a Grammy in that category this year for the audio version of his book, "The Audacity Of Hope: Thoughts On Reclaiming The American Dream."
Genealogist Christopher Child said that while the candidates often focus on pointing out differences between them, their ancestry shows they are more alike than they think.
"It shows that lots of different people can be related, people you wouldn't necessarily expect," Child said.
Obama has a prolific presidential lineage that features Democrats and Republicans. His distant cousins include President George W. Bush and his father, George H.W. Bush, Gerald Ford, Lyndon Johnson, Harry S. Truman and James Madison. Other Obama cousins include Vice President Dick Cheney, British Prime Minister Sir Winston Churchill and Civil War General Robert E. Lee.
Obama often jokes about his cousin Cheney at campaign appearances.
"His kinships are across the political spectrum," Child said.
Child has spent the last three years tracing the candidates' genealogy, along with senior research scholar Gary Boyd Roberts, author of the 1989 book, "Ancestors of American Presidents."
Clinton's distant cousins include beatnik author Jack Kerouac and Camilla Parker-Bowles, wife of Prince Charles of England.
McCain's ancestry was more difficult to trace because records on his relatives were not as complete as records for the families of Obama and Clinton, Child said.
Obama and President Bush are 10th cousins, once removed, linked by Samuel Hinkley of Cape Cod, who died in 1662.
Pitt and Obama are ninth cousins, linked by Edwin Hickman, who died in Virginia in 1769. Ben LaBolt, a spokesman for the Obama campaign, declined to comment on the senator's ancestry.
Clinton and Jolie are ninth cousins, twice removed, both related to Jean Cusson who died in St. Sulpice, Quebec, in 1718.
The New England Historic Genealogical Society, founded in 1845, is the oldest and largest nonprofit genealogical organization in the country.