With the way these series usually go, we can all guess that they're gonna actually fall for each other and be endgame. So when he starts getting serious with her he should also focus on winning over her siblings and aim to actually like them too, so when they awaken their powers he'll be fine with "sharing" her purifying powers. Like, if that happened imagine how strong of a family they'd be? With 3 magicians (one being like the fricken avatar) and a purifier, pretty much no one would be able to mess with them.
Like, c'mon guys (the characters), gotta think long-term not short-term lol