WASHINGTON — It would not make the happiest of family reunions. Senator Obama — the young, charming, anti-war presidential hopeful — is an eighth cousin of Vice President Cheney — the older, whiter, irascible warrior-politician.

The link between the two men was discovered by the vice president’s wife, Lynne Cheney, while researching her ancestry for a memoir about growing up in Wyoming.

“This is such an amazing American story that one ancestor … could be responsible down the family lines for lives that have taken such different and varied paths as Dick’s and Obama’s,” she told MSNBC. A spokesman for Ms. Cheney elaborated, explaining that Mr. Obama, currently the only black senator, is a descendent of Mareen Duvall, a 17th-century French Huguenot immigrant.

He married the granddaughter of a Richard Cheney, who arrived in Maryland in the late 1650s from England, and is a great-grandfather many times over to the current vice-president.

But if the 46-year-old senator doesn’t win the nomination, he could end up emulating his distant cousin if Senator Clinton, likely to be chosen as the Democratic party’s candidate, selects him as her running mate.

Mr. Obama already has an interesting past. He was born to a white American mother Ann Dunham and a Kenyan father, who separated when he was two.

He spent some of his youth in Indonesia before returning to Hawaii to be raised by his maternal grandparents.

A few months ago, it emerged that he is 11th cousin to President Bush, through another ancestral line going back to a Samuel Hinckley and Sarah Soole Hinckley in 17th-century Massachusetts.

But the connection to Mr. Cheney was news to the senator, who declined to comment.

A spokesman for Mr. Obama, however, said: “Every family has a black sheep.”