Hello thur.

In addition to your hard-ass step-brother I have!

Eugene Scamander and Jesse Hatchitt in his age range, Eugene more likely as he's a little looser in propriety than Jess, but Jess was an asshat in school, so they could still be bros. They both played quidditch too.

Bronwyn Moony fits your ideal "past antagonistic lover" mode perfectly. Like that is her. Her life's blood. And they might have known one another at school.

I think that's it XD