Hmmm, if you try to use your 3 year old child to bribe him to stay, it will only make him want to leave faster. You need to sit down with him and have a proper conversation and see if you can salvage anything from what is obviously a failed relationship. But , really, you should have brought it up long before it got to this stage as once its passed a certain point, there is usually no return as the decision is already implanted in his head. I bet he would have met someone else by now also...