I see. When I say "match", I think I was misled by this sentence "If you want to contribute to your child's Roth IRA or match your child's contributions, that's fine as long as she has at least as much earned income as the total contribution amount" in this page: https://www.nerdwallet.com/article/investing/why-your-kid-needs-a-roth-ira
Now I think it means that, the money that goes to the kid's Roth IRA doesn't have to be the exact money that she earned - kids can spends their earned money, and the parents can contribute that same (or smaller) amount instead.
