(CNN) -- Perhaps, now the candidates will play nice.

For all their insistence on how unlike they are from one another, the three U.S. presidential candidates share some noteworthy family connections, the New England Historic Genealogical Society has found.

Democratic Sen. Barack Obama, who has made his opposition to the Iraq war a linchpin of his campaign, is distantly related not only to President George W. Bush but also to another wartime leader -- former British Prime Minister Winston Churchill.

Because of his shared ancestry with President Bush, Obama is also indirectly related to his rival on the Republican side, Sen. John McCain.

McCain, it turns out, is a sixth cousin of First Lady Laura Bush.

Meanwhile, Sen. Hillary Clinton, is related to beatnik author Jack Kerouac, Canadian Prime Minster Pierre Trudeau and Camilla Parker-Bowles, wife of Prince Charles of England.

Clinton also shares ancestors with Grammy Award-winning singers Celine Dion and Madonna.

The senator won a Best Spoken Word Grammy for the audio version of her book, "It Takes a Village." Rival Obama also snagged one in the same category for his book "The Audacity of Hope."

Don't Miss

Conservatives who sometimes accuse Democrats of being in bed with liberal Hollywood elites may have been handed one more round of ammunition by the Society's findings.

Clinton, the Society said, is related to Angelina Jolie. And Obama is related to Jolie's boyfriend Brad Pitt. Watch a report on the candidates' family trees and other news »

The New England Historic Genealogical Society, founded in 1845, says it is the oldest such organization in the country. Members spent three years tracing the lineage of the candidates.

Among its other findings:

McCain, the Vietnam War veteran who spent five years as a prisoner of war, descends from a long line of kings: Scottish King William the Lion, English King Edward I and French King Louis VII.

Obama, the son of a white woman from Kansas and a black man from Kenya, is "related to millions of contemporary Americans - perhaps even a significant percentage of the population," the researchers said.

He is cousins with six U.S presidents, including Lyndon Johnson, Harry Truman and Gerald Ford. He is also linked to American artist Georgia O'Keefe, the Duchess of Windsor and two men who signed the Declaration of Independence.

Most surprisingly, Obama -- the man who could become America's first African-American president -- is linked by ancestry to Robert E. Lee, who commanded the armies of the Southern slave-holding states during the American civil war.

Bedfellows, it turns out, make for strange politics. E-mail to a friend

All About Jack Kerouac • Celine Dion • Winston Churchill