On the ship we were on some rooms had a pull down bunk. But the bed under it was a full size pull out not a twin converted couch like
DCL. So it took up a lot more space in the room and the room steward would not pull out the lower bed and pull the bunk down. So either both kids had to sleep in the same full size or one had the bunk and the other had the couch-as a couch not as a bed.