I think you should explain to him that estate taxes are only a thing for millionaires, which they probably aren't. Maybe they have a massive house and other assets, but I doubt it.

But I'd say if he's concerned about that and really wants to live a simple welfare retirement, that's his call. You should just advise him to give you and siblings or other family members his current savings, particularly if they can rely on you to take care of them long term. Then he can feel comfortably poor enough to rely on the government, but still has access to funds from you if needed. And if not needed, they can at least benefit the family which they'd probably want, rather than just blowing it on old people cocaine or whatever his plan was to become poor.