I would also first check to see if he has Urinary Trac Infection.
Then if not...they usually stop after getting use to one another.Not only is it not fair to you but it isn't fair to the other cats.I bet they love you very much and there is a bond there just like your mom has with Colin.Unless she really doesn't care about yours or their feelings than I have no more advise for you.Except try to move out quicker.I'm sorry you have to go through this.