I just last week moved my 6 and 8 year olds back into their own rooms.
They have been in and out for years depending On our needs at that time.
Most recently they had been sleeping with me almost a year. Since dd2 was born.
They generally sleep exclusively with me until 3-4
When I had all 4 sleeping with me I had a queen a double and a single all in one room.
It only becomes a " problem" when someone decides before the child is ready that they are done with cosleeping.