In our old house my kids were in separate bedrooms, son was 4 and daughter was 2 ish before we moved. My lad was not good at sleeping and we had regular horrible nights of screaming and shouting (not just from him unfortunately :cry:).
When we moved house we put them in the same room with bunk beds, and it changed instantly! Everyone was more settled. Kids like to be in a room with someone.
My lad at 7 has now decided he doesn’t want to share with his sister so we’re doing up the spare room for him. I don’t think my daughter has realised yet and i don’t think she’ll like when she does!!