which of these do their kids gets saddled with?
Both? Neither would be impossible unless the kid had no powers, I've got the world-building there, but if they get only one set, do the powers match? Or at least if they mix and match, is there some kind of equivalence?
And which theory of the odd-ball weakness would it buttress? (If the heroine and troll-wife argue about it a lot -- I think I'm going to have to give the troll-wife a name.)