I think B/S, because many times in F/D the father seems too forceful, and I don't like that (But if M/S or M/D the mother can be as forceful as she want I'd find it hot Hahaha).
Brother/Sister is my favorite followed by father/daughter i never liked the mommy stuff
feels like fucking sloppy seconds to me I'd rather have my women fresh and unused
Brother/Sister, both version, old sister younger brother and the other way around. Of course if parents watch in secret or the other way is nice too...