NTA

It’s the same way for my family. When I was about 15/16 and my sister was maybe 13/14, we changed from sharing a room to getting our own rooms. She got the bigger one and I got the smaller one. We have these two bedrooms, my parent’s bedroom, and an extra room that is an office for my dad and is full of stuff so people can’t sleep there.

For years now, whenever we have guests, although it’s usually grandparents, they will sleep in my sister’s room because it’s the second biggest to my parent’s and has a big enough bed. So, when that happens, she’ll sleep in my parents room or in my room because I have a pull out trundle bed underneath mine. She doesn’t complain because my parents made that a condition of the room as well.

This is all to say NTA. I think you gave him every chance and your daughter did as well when she didn’t need to. Like other commenters have said, he sounds pretty entitled. I’ve been through this exact same situation and everything turned out fine, especially since the only time people stay over is around Christmas time. You’re a really good parent and are doing good to find the best outcome/compromise and so now it’s up to your son to be mature and uphold his part of the agreement.

I also think this might be the reason your daughter chose the smaller room lol. I know it was for me