Have you stopped to think that maybe he's trying to get attention precisely because he feels left out? Jealousy at that age is pretty physical, really - talking doesn't work because he's frustrated and needs to process it some other way.
Try putting something pretty specific into practice: when you notice he's starting to act out or get aggressive, instead of calling attention to it or punishing him, take him aside and suggest doing something together - it's not even a reward, just a ritual between you two. It could be helping you with something, sitting together for five minutes just the two of you, anything that shows "you matter and I have space for you too." It doesn't have to be long, but it needs to be consistent. His pattern of aggression usually drops when he stops competing for attention and starts feeling like he has a guaranteed place without having to fight for it.