Earlier quoted context omitted.
This was flagged, but I think mistakenly by people who think you're joking or taking a dig. The point is there weren't 70,000,000,000 people alive in Italy back then (or, you know, anywhere ever), so it is very likely that Dante shows up in multiple branches of this person's ancestry.
Which also implies everyone is a descendant of Dante.
You are right that in the infinite time limit, assuming nonzero mixing, either everybody or nobody will be Dante’s descendant.