I need help and advice.

I am engaged to wonderful woman, we have been together for about 8 years now. When we got together she was two months pregnant by her husband that she had recently left and her mother had custody of her two boys due to somethings that she had done years prior to us meeting and her and her husband not being able to get things straightened back out. Which along with being abusive is why she left him. She had finally had enough. Two years ago we won custody of the boys back from her mom and step dad. Since then the oldest has decided that he is not going to go to school, refuses to be a part of the family, treats everyone like crap, and only wants to back the other, bad, side of town and smoke pot, which he is not shy about at all. He hates my guts because I yell at him because he refuses to do anything productive and I just want him to apply himself, respect his family, try at anything besides being a punk. He is following in his fathers footsteps of being in and out of jail and on who knows what drugs. How in the world do I, we, get him redirected????