Boyfriends friends

First, Me and my boyfriend have a mutual like “best friend” and he doesnt want me to hang out with him alone, it’s the only guy he wouldn’t want it happening with. What does that mean? Second, me and the friend are pratically family, he’s probably the last out of my boyfriend’s friends to ever make a move on me. He’s there for me and always says like “morning beautiful”. My boyfriend previously got mad at a friend for this, do I tell the friend to stop?