Wizards of Waverly Place is really dark if you think about it
I used to watch this show with my daughter when she was growing up and I was scrolling saw it and a thought exploded into my mind.
The family wizarding competition applies to every family not just those where one of the parents is a mortal. At least in Jerry's family the kids are born and raised in the mortal world. Any one of his kids that doesn't win the competition will still have a reasonably good life in a world they know and love.
Full Wizard Families are having kids that have to go from a Wizard's life to a mortal's life with possibly no experience of what that's like effectively becoming a stranger in a strange land.
Every family that has more than one kid is condemning their other kids to losing not just their magic but all their friends, family and community.