We had this problem with our 3 year old a few months back. He would start out in his bed and then climb into ours. We were so tired we just didn't fight it. Eventually it was every night, and my husband couldn't stand it. We first turned his bed into an awesome cave. We draped a dark sheet over the top and tied it to the head and foot boards. We played in it with him during the day and kept talking about how cool it was. In just a few days, he was so excited to sleep in his new cave that he stopped coming to our bed. During those few days, if he came in to our room, we took him back and covered him up. Now he stays in his own bed every night. If he likes pirates, try turning it into a pirate ship. It works like a charm. Good luck. Trust me, he won't want to sleep with you forever.