Ahhhh, the birth order question. I have come to believe your birth order plays an important role in your life. But I also believe it is less relevant to your relationship with your birth family when you are raised by an N.....with one exception. I think generally the N is "closer" to their firstborn because traditionally they are able to pass along all their horrible narcissistic ways to the firstborn. Hence, the two develop a symbiotic relationship.
In my family, I'm the middle child...and hold many of the characteristics of most middle children. However, because I was raised by an N mother, a co-dependent father and have an older (firstborn) N sister, it has little relevance...It has little relevance because in an N family, I don't matter...Now if I was a firstborn but fought my Nmom's narcissistic ways and didn't transform into an N myself, I would be equally reviled by her and would not have gotten the GC role my Nmom has showered on my Nsis.
The truth of the matter is that when you're raised in an N household, it doesn't matter if you're the first, second, third or fourth child, the Nparent doesn't care about you and will not pay any healthy attention to you....In an N household, I think it's less about your birth order, than your personality and other circumstances (such as whether you were lucky enough to receive attention from non-family members or others who showed you love or interest). In my case, I was not...so my lack of self-esteem and self-loathing was complete. However, my brother, the baby, got attention from my Nsis who made him "hers" growing up as well as a number of friends who showed him he was worthy. My Nsis (the GC and firstborn) of course got literally all my parents' attention. In addition, in her adult life, she found a co-dependent partner who fostered and enabled her narcissistic ways.
While birth order does effect us some, the fact that we were raised in truly unhealthy, dysfunctional families by a N parent(s) who was incapable of demonstrating love, care or interest, cancels out any consequences of birth order. The damage we experience as a result of being raised by an N is far more significant than that experienced by firstborn, middle or lastborn children of healthy families.