How would you take this?

My fiancé and I have been together for 5 years and have lived happily together for 4. I have a 7 year old girl from a previous marriage and his son is 9. We are currently building a shop with small living quarters where we will stay while the house is being built. It has a loft where the kids will play and sleep when we have them. I have my daughter every other week for a week at a time and he has his son every other weekend. He had the nerve to tell his son “this will be just your room, but you have to share with “my daughters name”. He does these types of things all the time and it pisses me off. I have worked hard and have been apart of this right from the start, and I just think it’s bullshit. The kids will both have their own rooms in our house. I’m not looking for someone to tell me to talk to him about it because I already have, I just want an outsiders point of view. Thanks.