F/D and B/S are my favorites, but U/N and A/N are also pretty fun dynamics. Weirdly I'm not into M/S, which might be the most popular one. I won't turn down a game because it has M/S in it, especially if its well written, but the scenario itself doesn't really do anything for me.
Maybe it's not quite my thing, but B/S and A/N, possibly because they're less direct. I do like S/S or M/D when I'm a third character getting the other characters to participate.
Depends on game. Am I playing as young MC or older MC?
Young MC- mother, sister(s), and aunt(s).
Older MC- daughter(s), sister(s) and SIL (not sure if that counts as incest)