You are 16. Tell him he stays out of your room or he gets reported to Police. Get some pepper spray and zap him if he walks into your room. Everyone has the right to privacy, heck I knock before going into my 12 year old sons room.Tell your mother she better do something about him as you don't feel safe and have concerns about your younger sister, if she does nothing you will report her to social services. you say on another thread you have had experience of adoption? So this is your adopted mother?