I have two DS's ages 10 and 7 and a DD age 5. My DS's share the bigger bedroom whilst DD had the box room. Recently DS1 has been complaining about having to share with DS2 and is asking to have the box room and DS2 and DD share instead. I'm starting to think it's not a bad idea, they tend to get on better and spend more time together, the boys argue a lot, especially over their bedroom. I'm not sure how DD will do with sharing as she's always had her own room but I'm thinking it might help her stay in her own bed rather than getting in mine (probably not). DS2 isn't fussed about sharing he's never really complained about it. I'm hoping to move in the near future hopefully to a bigger house so it wouldn't be a permanent arrangement