I'm the fourth of 5 kids, 2 brothers, two sisters. We're 35, 31, 28, 24, and 22 years of age, currently.
The family dynamics tended to change fairly often, since my parents divorced in '97 and my dad was out of the picture a few years later.
I would say it helped and hindered, having five of us. We sort of raised each other, but of course there were more mouths to feed. I would often think to myself, my mother shouldn't have kept on having kids, if she didn't plan on taking care of them. As the older siblings left (for instance, the second oldest left at 16, I was happy she got out) the responsibilities would tend to shift. When the aforementioned sister left I was 9, and the "mantle of responsibility" skipped my other sister, the middle child, and went to me. I would try to make sure my siblings were fed and taken care of, and that the household didn't completely fall apart. I still often have to remind myself, to not neglect my own needs, and spend too much time worrying about others.
Still, I love my siblings and have been, and will continue to be, with them throughout their darkest moments. I've said before on here that I don't think family is bound by blood, but it can include it. There are members of my family I have no desire to see, and haven't seen in years. I feel no obligation to include them in my life just because we share genes. My siblings are family because we're there for each other, because we've stood together in the face of opposition and fought for each other. We don't talk as often as we used to, but they know if they ever need anything all they have to do is call.
Despite everything, the ups and the downs, I am glad for the "family dynamics" we had. I've learned much from my siblings, and we continue to educate each other. Perpetual students. I might be reserved, much of the time, but they've helped me open my heart.