Thank you all for your outpouring of support and encouragement---it truly means a lot to me. I, too, have often pondered the question of why my brother and I turned out so differently from our other siblings, and vunil, I think you might be on to something.
My brother and I are the oldest children in our family, and there is a big gap in age between the oldest and the youngest. For years, my brother and I talked about the presence of "two separate families" within our family. We may share the same DNA with the other three siblings, but we are WORLDS apart re: how we interact with the rest of humanity.
Our parents were extremely strict and punitive when we were young. Any minor infraction that my brother and I committed(like forgetting to say "please" out in public) was treated like a crime against humanity. Our parents were quick to remind us that THEY were in control---we were more like their subjects than their children. The prevailing parenting dynamic during those years was one of "good cop, bad cop," and the relationship we had with our parents was dictated by fear.
Vunil, what you proposed (re: the child reared in an oppressive environment being less likely to act on N impulses) really grabbed my attention. My parents were quick to put me down if they thought that I was conducting myself in a manner they found to be "inappropriate"(i.e., acting like a child my age, rather than the little trophy child automaton that they aspired to have). When we were growing up, our parents were on my brother and me like flies on poop.
When the other siblings arrived, our parents were that much older and they took a laissez faire attitude in rearing the younger kids. By that time, my father had also retired from his high-stress job and was far more approachable with the other kids than how he had been toward my brother and me. I would have to say that the absolute worst N in our family is my youngest sister. This is where the question of genetics comes in, because I can remember my sister from the very beginning of her existence, and as soon as she was old enough to have a personality emerge, she was a mean child. She took delight in gossiping about other family members and passing along hurtful information from one sibling to another("do you know what 'so-and-so' said about you?"). Because my mother indulged her(she was the "baby," and to this day, my mother still treats her this way), my sister's N behavior ran rampant, as it continues to do to this day. My other two younger siblings exhibit similar traits, but not nearly to the degree that my youngest sister does.
One thing still blows my mind: because our parents have projected their attitudes about my brother and me onto our younger siblings(i.e., their use of control and intimidation to try and get us to conform to meet their needs), our younger siblings obviously believe that they, too, have a right to use this approach when dealing with my brother and me. The obnoxious attitude of entitlement that they take with us is sickening, like my brother and I owe them something.
Mudpup, I appreciate your "suggestion" for my brother---believe me, I had the same thoughts! ; )