It sounds to me like you've already identified the cause and reasonable strategies to use with your son(s). Giving the boys equal and individual attention is important, but so is the cooperative time you all spend just "being together".
The son who is "acting out" may be coping with his own emotions, not yet knowing how to "verbalize" or even "label" what it means to be sad, afraid, frustrated or confused.
He may be yearning for his twin to play and do the same things he does. It is amazing what empathy brothers can have for each other, even at such a young age. My two sons are actually 18 months apart, but the older one would always cry when his younger brother was hurt, hungry, irritated etc. To this day, he still comes to his brother's rescue and "looks after him". As they get older, gentle reminders to let the younger one think, do and answer for himself will come more into play.
Also, one of the biggest hurdles I ever had to get over, and still work on today, is that boys are naturally more physical and aggressive in their play, thought processing, and general movement. I often say that if I could move the way my 6 & 7 year old boys do, I'd be so thin because they are always on the go. I'd suggest observing how the older plays "with" and "without" his brother and listen to the things he says. I believe you are on the right track with everything and I applaud anyone who has multiples!