L.M.
My middle child (girl) and youngest (boy) shared a room and bed by choice from the time he was about 2 yrs. old and she was then 6ish up until 1 1/2 yrs. ago. He is now nearly 7 and she's nearly 12. They still have a great bond and it was sweet to walk in and see them all snuggled together. There were only a few times when one would complain that the other took up too much room on the twin bed. Other than that, we had no problems. I think most kids will start to complain or wish for their own room when they are ready to. I know some people frown on opposite sexes sharing, and I think def. by the time puberty hits, they should be separated, as that's when most kids want privacy and space.