You say you have been screwed by adultery before. Would you mind taking a moment to explain why he was allowed to even get behind you, kissing you, trying to pinch your nipples? Shouldn't you have just pushed him away, rather than giggling like a 'woman' who doesn't really care about wrecking a relationship with 'her' sister?
Congrats for not fucking him or doing anything, but I would suggest you limit your time with him for a bit, because he should understand that being a cheating bastard isn't the thing to do, no matter how much booze he's had.