In this screenshot I took from an Abstergo Entertainment discussion from AC4, it names ancestors of Desmond's on both the patrilineal and matrilineal lines. As you can see, someone on the matrilinial line was alive during the French Revolution. Since we know Arno isn't related to Desmond, who do you think this could be. Do you think Arno ever met him/her?
File:Assassin's Creed® IV Black Flag 20150908170402.jpg
(Please let me know if I'm using the forums incorrectly, I'm new to them.)