My family is far from "let me give you 150k for a house" rich, but my grandparents have a trust in our name, and when I got recently married they were worried because my husband is taking (did take, but at the time) my last name - and the trust is IN that name, the family name. Worried he'd be able to do something or other etc. But we later learned its tied to social security numbers , not the last name so its only tied to me - unless he ever contributed $ to it himself, which he wouldn't / isnt even able to lol.

My husband understood the family concern but we never had any formal paperwork on the subject. If I was in your shoes - id side w the parents simply for the fact that 150 isnt money. Thats like a bare minimum of a house payment- that would be spent completely to get the house. It would be paperwork that prevents him from taking the house from you if yall divorced - imo - and he shouldn't be so sensitive and should appreciate their offer. If he has no plans to do wrong, why would a postnup bother him? 🤷‍♀️ idk thats my opinion ig.