I just asked this question about my daughter on here not too long ago and I received some advice that has really worked wonders for us. My daughter was starting to scratch and hit the daycare children that I watch and I couldn't keep sending them home with marks all over them because of MY daughter. This is what the advice was:
Give the child who gets hurt all of the attention. Comfort the child and tell them you are sorry that they got hurt. Give the child lots of hugs and kisses and when you are done quietly go over to your son and say, "Please use nice hands and please use your words." Walk away. Oh my goodness!!!! This worked! My daughter has hardly been hitting and scratching this past week and I feel that she is now seeking more positive attention. I, too, am learning to recognize when she is needing more attention and I give her lots of hugs and kisses and try to sit and play with just her at least twice a day. When I see that she is getting out of control, I have her come help me with something that I am doing to redirect her. I would have never thought of this tactic, but I loved the advice and it ended up working. Good luck.
As for your other post, try setting a timer for the amount of time you feel that your younger son can withstand the rough housing. When the timer goes off, have another 'active' game ready for them to play since they will still have plenty of energy to burn off. We will play follow the leader, simon says, build with the couch cushions, play red light green light, etc. when things are getting pretty wild:)