Sleeping arrangements in 3 bd house with 5 people in it?

Put the 2 boys in together as your daughter will be a teenager in a couple of years and won't want little brother sharing her room. Also I think it is not a good idea to have children of different es share a room when one of them is over 10. Your 9 year old will soon learn to play nicely with his little brother and as they both grow up, they will become closer. Using your sitting room as a bedroom as well as a sitting room is also not a good idea as you will be constantly changing the room from one thing to another.