Already seen this a few times with people I've dated.
Rich parents buy a vacation house, not so rich kids pay rent on it with no equity while also understanding that their shitstain parents will reverse mortgage all that equity for retirement vacations before they ever have a chance to inherit it.
They cope with a 'this is fine' attitude.
If I had a nickle for every person I dated that was in this situation, I'd have three nickles. Which isn't a lot, but it's weird it happened three times.
To be fair, if they're bringing home a paycheck they should be contributing. Of course since it's family you do a split based on income, not a straight split. And they also get a say on things around the home at that point too.