His paternal grandfather converted. This hardly constitutes "his ancestry."
That makes him more likely the descendent of slave traders than of slaves.
If you go back far enough, most of us and quite possibly all of us are descended from both. Why it is relevant is beyond me.
> Why it is relevant is beyond me.
Perhaps the irony escapes you.
None of my ancestors owned slaves ... at least for the past 1000 years. They were poor serfs and lived under oppression as far back as we can look.