You cant control people or what they do. And if you are not happy, or the situation makes you uncomfortable/aggitated why do you choose to stay? You are creating your own drama. If you think you can tell people how to behave and they will listen you are wrong. Relationships are two sided. If your boyfriend chooses not to give up his friendship with his ex that is his choice. If you dont like it you need to deal with it on your own circumstances. He is an individual. Not a dog that you can train to behave on your terms.