How should i help my brother?

kind of a long story but ill give a little bit of a background my mom was a big drug addict and prostitute and alchoholic. always changings bfs and homes. she lost custody of all five of us brothers. i went to live with my dad and grew up in an abusive home so i moved out lived with my mom at 17 and found she was still doing drugs and drinking and she had just gotten out of prison but she wasnt prostituting anymore but she couldnt keep a steady home or bf. i moved 10 times in a year and a half. i moved out and moved in with my fiance. so far one brother i cannot locate cuz his foster parents dont want him to know what his old family is they even changed his name hes about 8 or 9. my second youngest brother his father wont let me see him after i heard he tried killing himself hes about 10 or 11. the brother i found last week is 18 and hes currently going to collage for culinary arts same as im trying to do him and i talk everyday. the brother that worries me the most is my brother thats 16. i got ahold of him last night after i heard that he was having contact via fb with my mother eventhough her rights were terminated and she was illegally talking to him. hes doing drugs and running away and breaking into houses and steals from his own family. i made plans to have him stay the night monday. how should i go about helping him and should i let him know what our mother was like when i lived with her the last two years. he thinks that she will give him everything she promises even tho she cannot even take care of herself and she is dieing from so much drugs. shes had me sell drugs for her and shes offered me drugs and has caused so many problems and pain i dont even talk to her anymore and never will again. and neither will my 18 year old brother but how should i help my 16 year old brother"?