For example, christianity ultimately is an offshoot of judaism. Some stories are exactly the same, the ones in the Old Testament, unlike this question, where there is a lot of cultural overlap but the stories aren't from the same first source. Other stories in christianity aren't in judaism at all, though, obviously.
So what should a question like: Who did Adam and Eve's son Cain marry? be tagged? christianity? judaism? Both? judeo-christian? old-testament?
I'm just brainstorming here. I welcome all thoughts from the community.
Update: We now have abrahamic-religions. I don't know if that adds any clarity or not.