Afaik Lilith is apocryphal in Christianity and in Judaism and is mostly relevant in some occult Jewish traditions. She's not part of the main stream religion or theology in either case.

I've never seen anything to indicate that ancient Hebrews were particularly concerned with the question of who ended up marrying Cain, Able, and their descendants. There are lots of putative genealogies out there, so you could look up some of the old ones, but I think the Genesis narrative just didn't consider the question of where the wives of the first generation came from to be important to the narrative.