User blog comment:Nakedsnake53/Brotherhood Ending SPOILERS!!/@comment-3260702-20101209173814

As you see in the beginning of AC:B, Caterina Sforza was in bed with Ezio. If she has a child, but hides it from Ezio & all of the Assassin's order, he could be another ancestor.

But seeing as AC III will have an entirely new storyline with other main characters, it's probably going to be something completely different.