Welcome to SR,
I am a mother of an recovering addict. I wish someone cared enough about me and my son to tell me he was an addict. I found out when I told him to leave, and by then it was to late, he stole so much from me. You can do nothing to make him stop, but if you feel you need to do something tell him parents. If they don't believe it, it isn't your fault they are in denial. Please attend either Nar-Anon or Al-Anon meetings, you will find support there also.
Keep posting and reading you will find support here
Hugs coming to you