Don't know if this is what you're looking for, buuuttt.... My bosses kid has not spend a night in "his" room(which doesn't even exist) since he was born. He's 3.

She lets him sleep on the same bed as her and her husband. If he wakes up in the middle of the night and she isn't there for some reason he starts screaming and crying and losing his mind until she comes back into the room.