Family fee - just an Idea, would that work?

[Akonyl]

All those things can faked fairly easily. That's why I'm saying DNA testing is the only legitimate way of proving relations. Even living in the same house doesn't prove you're related. Lots of pro gamer teams share housing. Plus, I'm not giving any of my personal documents to a gaming company, and I don't think many people would want to do that.

DNA's still pretty bad, because it has the unfortunate effect of singling out families with adopted children too. There probably aren't any good ways to do this that SE would ever care to do, really.

[HumanNinjaToo]

DNA's still pretty bad, because it has the unfortunate effect of singling out families with adopted children too. There probably aren't any good ways to do this that SE would ever care to do, really.

Exactly, there is no way to make this work effectively, which is most likely why it's 2019 and has never been implemented in any long-term business models for subscription services.

The exception being cellular service plans. And even though they are called family plans, you don't have to be family, you just agree to let one person pay the bill for everyone on the plan.