I had this problem with my older sister. Whenever my mother left my sister in charge, I refused to listen to anything she had to say because she is sister. She's not my mother. In your situation, he is living with you, so you need let him know that you are in charge. You are responsible for him now. Just sit down and talk to him. Let him express his feelings. Tell him what you will and will not tolerate. It is best for him to have a little freedom, but make sure he doesn't abuse it. If he doesn't have any freedom at all, he will definitely rebel.
The administrator has disabled public write access.