WASHINGTON —  Democrat Barack Obama, who would be the first black president if elected, also has white ancestors who owned slaves, according to a genealogical researcher.

The researcher, William Addams Reitwiesner, says the discovery is part of his first draft of research into Obama's roots. Obama's father was from Kenya and his mother was a white woman from Kansas.

Obama wrote in his autobiography, "Dreams from My Father," that while one of his great-great-grandfathers was a decorated Union soldier, family rumors also say he is distantly related to Jefferson Davis, president of the Confederacy.

Reitwiesner found in 1850 Census records from Kentucky that one of Obama's great-great-great-great grandfathers, George Washington Overall, owned a 15-year-old girl and a 25-year-old man. The same records show that one of Obama's great-great-great-great-great-grandmothers, Mary Duvall, also owned two black slaves — a 60-year-old man and a 58-year-old woman.

The Baltimore Sun first reported Reitwiesner's work and asked genealogical experts to review it, but they would not confirm the findings.

Obama spokesman Bill Burton said the senator's ancestors "are representative of America."

"While a relative owned slaves, another fought for the Union in the Civil War," Burton said. "And it is a true measure of progress that the descendant of a slave owner would come to marry a student from Kenya and produce a son who would grow up to be a candidate for president of the United States."

Reitwiesner found that two other presidential candidates were descendants of slave owners — Republican John McCain and Democrat John Edwards.

The New York Daily News reported recently that genealogists found that relatives of former segregationist Sen. Strom Thurmond appear to have owned the ancestors of civil rights activist Al Sharpton.