Well the easiest thing to do is sit down with your parents and ex spouse and discuss and see what would be the best arrangement for all of you. If it were myself and I felt uncomfortable, I would probably move out if my parents insisted to allow the ex to stay. If you believe you are in imminent danger to be in the same space as your ex I would consider contacting a lawyer about a restraining order if you feel your life is in danger. Other then that I hate to say it, but suck it up and live with the situation since you don't own the home you are living in.