Remus
As long as he doesn't get famous perfecting this potion while exposing you, we'll be fine. Yes, he's much to clever for that.
The less said about those times, the better, my friend. But you're right. Relationships are messy, there's no avoiding that.
Is he though? Granted, I haven't spoken to him, but he was never the type to acknowledge he'd made a mistake. It was always someone else's fault, or someone else's actions that were the mistake. Has that changed? If he truly loved his brother, he'd realize it was their parents who let the Black family name down, treating them they way they did, Sirius especially though I doubt Regulus was free from that treatment himself.
Butterbeer? I go for Whiskey when dealing wiht the Black family drama.
Oh, did you see that Lucius Malfoy has a bastard son? He's 11, a Slytherin, and apparently looks just like Lucius. You probably have him in class.