My 15 year old son is moving back to live with me. I need advice on making it a smooth transition.?

He has been living with my ex-husband for the last 5 years and they fight bad! Neither one is happy. My present husband and I are prepared to have him move in with us and change custody. However, my 14 year old step-son is not happy and I think is jealous. (we see my step-sons on weekends) My husband is wary of this change too, thinking that it is going to put a lot of stress and headache on our relationship. I almost lost my husband before over this, but I want my son to be here with me. My son and I have a very good relationship; he isn't dis-respectful or y. He just needs to work harder in school. I feel lost and alone during this period, as I feel I am the only one that sees this as a positive change for my son and myself (to finally be his mother full-time) I need advice on how to make the transition smooth for my two step sons, and my husband. My son desperately wants to live here with us and is excited. I don't want him to come into a resentful home by others. HELP!