User blog comment:Subject 16*/Assassin's Creed: Revelations - News/@comment-3097746-20110529034535/@comment-1655340-20110530021518

In ACII, when Lucy is downloading the content of the Animus to give to Rebecca at the hideout, in order to do so, she has to sync with the last user: Subject 16. As it syncs, it comes to the earliest ancestor common to both Subject 16 and Desmond: Ezio, which starts with his birth (not his conception, which it really should have started at if it is true that you can't view memories after the "torch is passed" to the next generation). So, the two are related through Ezio, which means that Ezio couldn't have had only one child, otherwise it would have synced to him or her instead of Ezio. So, either Ezio has twins, or has the two possibly bydifferent mothers, allowing Ezio to still relate the two (Desmond and Subject 16), but only half-way.