For Obama, he is not descended from slaves. I guess it depends on who they define as eligible for reparations. I don't know that I have ever heard that defined.
That's not the point. The point is, some people honestly believe that a guy everyone (if they knew nothing about his parents) would describe as black/African-American is "really white," just because his mother is. So how would you convince those kinds of voters that people like Key & Peele (both half-black, half-white, so they're "really white") should be getting reparations?