I would suggest your spending as much time alone with him as you can, offering him physical affection, encouraging words, and understanding. Try to convey in language he will understand that you understand his frustrations. Give him as many choices and alternatives in his daily life as you can as he is craving to show his independence and power. Siblings Without Rivalry, by Faber and Mazlish and Loving Each One the Best, by Nancy Samalin, will be very helpful as you raise these sons.
Language will come easier to him soon and his frustration level due to this problem, will be greatly diminished. Yes, there are different issues that kids have based on birth order. But that does not mean that you are doomed to endure some version of what you are dealing with now for the rest of their lives. It's just more difficult at this stage because of their specific ages and stages. If you really feel you are losing your ability to have patience, I'd suggest some short term family therapy for support.