Give Me Some Credit
Sirius Black has always been a player, a fuckboy, and it's never been a problem; he has his rules and the biggest one is keeping his hook-ups separate from his friends.
So how complicated could it possibly get when he starts sleeping with Remus Lupin? Who, unbeknownst to him, is his brother's roommate and best friend. Of course, if anyone could manage it, it would be Sirius - though that's easier said than done when James (his best friend and roommate) starts dating Regulus.
And just in case that drama wasn't enough to entice you, Dorcas and Marlene are our resident cutesy lesbians. And Lily and Mary are obliviously pining.