Hi and welcome to the board.
I'm Lori, sahm to 9 yr old twins, an 8 yr old and a 4 yr old.
I don't have any advice for you. We still have problems with my 4 yr old climbing into bed with us or her big sisters.
We didn't have any problems with our twins when the were that age. They have always shared a room and we had a special double-sized crib for them until they were 2, then we moved them into their own beds and they have slept alone since.
Sorry I don't have any advice, maybe another member will have some ideas for you.