I'm betting if they can, they are going to make that the Abel who is the preincarnation of Fei. The fact that he looks just like Fei and the fact that his name is Abel is way too much of a coincidence.

On the Nephilim thing though, as I understand it Elly was based off a girl Abel had met earlier, who is supposedly the daughter of the Captain of the Eldridge (you see him open a picture of his wife and daughter, both of whom look like Elly before the ship goes down).

Anyway, Kos-mos could very well be Deus, so it's not at all inconceiveable that Abel is indeed the Abel that eventually reincarnates as Fei.