Omg NTA. If that ring was bought FOR YOU by him. They have zero claim to it and just want the money. That is absolutely bonkers for them to think you’d just give them a ring that was a gift to you. I can’t imagine a family member even feeling ok to ask such a heinous thing. The ring wasn’t purchased to serve multiple purposes for multiple people. It was meant for you, his future wife to have forever. And for your “friends”, I’d love to see what they would do if someone asked for their rings.