Well, a lot has to do with the home environment and how the parents make an effort to make sure each child gets what they need. The OP has not talked about how his mother was or what his home environment was growing up, at least not in this thread. But, what I do see is how threatened he is by his younger brother or anyone that is like his younger brother. It seems to me that he gets triggered and this trigger goes way back for him and that is where he could use some help. Even his feeling unappreciated probably goes way back for him as well and he has not realized that in a way that could be very helpful to him.