I'm looking for a fic where Charles has a boyfriend - OC, can't remember the name, and his boyfriend's brother is Erik who lives with them for a while. And Erik is this disreputable, kind of 'bad boy' and Charles doesn't like him at all at first.

I remember the prompt having a youtube link to Fassbender's sex scene in Fish Tank, and that's what inspired the fic because there's a part in the fic that Charles cheats on his boyfriend with Erik. I remember reading it on AO3, but seeing the prompt either on xmen-firstkink, or 1stclasskink.

The fic ends with Erik just leaving and Charles' boyfriend being oblivious and like "see that wasn't so bad, he's gone now."

I'm sorry if this is super unclear, but I seriously seriously can't find it it'd be awesome if someone could link me it!