The New York Times recently published a story about about President Obama’s likely descent from the first recorded slave in the North American colonies. The keyword here is "likely." The claim is lacking definitive proof and simply says, "evidence strongly suggests.” In fact, this isn't news. If you go back enough years, everyone is descended from most everyone.
After all, you have two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents, and so on in a straight mathematical progression. If you go back 300 years, you have about 4,000 ancestors, assuming no duplicates. If you go back a thousand years, and each of us theoretically has more than a trillion direct ancestors, again assuming no duplicates. Of course, all of us have duplicates.
Now add in an unknown number of aunts, uncles, and cousins, and you have perhaps hundreds of thousands of relatives. There's bound to be somebody famous or infamous in a group of that size!