Washington ? Rush Limbaugh calls President Barack Obama “imam,” even though he knows the president isn’t a Muslim. Sarah Palin has openly doubted the president’s “cojones.”

Turns out these two conservative firebrands have been dissin’ their own cousin.

The online genealogy service Ancestry.com now reports that Obama and Palin are 10th cousins, and Obama and Limbaugh are 10th cousins once removed. In both cases, the ties date to the 1600s.

Obama’s distant family ties to former President George W. Bush and former Vice President Dick Cheney surfaced during his presidential campaign. Obama also is a distant cousin of billionaire investor Warren Buffett and actor Brad Pitt, according to Ancestry.com.

Anastasia Tyler, the lead genealogist on the latest project, said in an interview: “It just shows how all of these politicians, they’re on different sides of the political spectrum, but in the end they’re all part of what makes America great, and they all go back to deep American roots.”

The ties run through Obama’s white, Kansas-born mother’s side of the family. Obama’s Kenyan father’s background is harder to document as far back, and likely would have fewer connections to early American settlers. Genealogists say it’s typically harder for African-Americans and many minority populations in the U.S. to trace their roots because of a lack of written historical documentation.

Palin’s tie to Obama is through early Massachusetts settler John Smith, a Protestant pastor in the 1670s who opposed the persecution of Quakers. Smith’s wife was the sister of one of the first governors of the Plymouth Bay colony, Thomas Hinckley. Hinckley’s father, Samuel, it so happens, is the familial link between Obama and Bush.

Obama’s and Limbaugh’s common ancestor is Richmond Terrell, who settled in Virginia around 1656 and acquired a large amount of land.