I am sorry too that you have to be here, but this is a good place for support. The thing is, his mom and sister may have influenced him, but they did not force him to relapse. He is in full control of his addiction. A H addiction just like an alcohol addiction is just that...an addiction for life. From what I have heard and read, H takes over their lives above all else. He has to want recovery and unfortunately it sounds like he has no interest at this point at all. You cannot will it for him.
It will cause you much less pain to move on from him and let him deal with his own addiction in my opinion.
I am so sorry.
Keep posting, you are not alone!