Henry Thompsett could be a possible protégé candidate. He loves quidditch and he's the youngest of his family with a mostly absent father especially since his mother died. We can have a few summer threads and see how the dynamic works. Even if he doesn't fit what you have in mind, I have no problems threading anyway.

Potential mistress... Steliana Nicolescu though she's not the sort to sleep around and is wealthy enough she can buy her own wealthy things but that doesn't mean she won't warm up to flirting. More of a play it by ear sort of thing, then again most romance I prefer to be developed in game.