To be sure in slavery times it was no doubt uncommon that slaves engages in "relationships" with their owners. They can either be mutual or not I imagine. Most of us don't know what might show up in our genetic family trees. All I know is that I do have a Native American ancestor.
I would question why this could be news but I don't know this is still an interesting revelation.
Sharpton, Thurmond, and Slavery Ties by My Urban Report
Who Cares? by Second City Cop