This is just lovely, really well done. You've characterized them all so perfectly: James, cocky, bright, and, underneath it all, supportive; Sirius, charming and bold with an appealing touch of insecurity; and Remus -- kind, wry, vulnerable, and so likable.

All sorts of great lines, too --

but you’re a sixteen-year-old boy just like the rest of us, even if you act like Dumbledore’s older brother half the time.
Hahaha!

The truth was out there, now, and it was both a terrible feeling and a good one.
Yep, just how it feels.

“Yes?” It comes out about an octave higher than usual.
Ha! I can just hear him.