I'm lucky in that I have a very close friend who grew up in a startlingly similar family situation as I did; it's great for comparisons such as these.
He and I are 3 days apart in age, and the eldest of 4 kids. Our sisters are 3 years younger, our brothers are 5 years younger, and our youngest sisters are 7 (him) and 8 (me) years younger.
He: ENFP with ENFP mom and INTJ dad.
Me: INTJ with ENFP dad and ISFJ mom.
Basically, we both agree that our younger siblings get away with more than we did at their age, and also that as our parents get more practiced, it shows with their parenting skills. We both feel we had to "work them in" yet didn't reap the benefits because it took a while for our parents to get the hang of things.
From our conversations, I had the harder time of us two considering the fact that I grew up in a household full of very xxFx types (my iNtJ being a small "t" is learned, not natural). Our youngest sisters are both xSFJs, and I don't see any correlation to sibling order regarding intellectual independence, only MBTI.