I just realised, thanks to the wonders of Facebook, that both my oldest first cousin and my youngest first cousin have birthdays today. The one is about 40 and the other about 20. My mother is the oldest of nine children, and I am the oldest of my grandfather's grandchildren (he was married twice). Altogether there are 22 of us, with I think about 17 in the next generation so far (my own three children, my two nieces, and a dozen offspring of our other cousins). I don't think we have ever all been in the same place at the same time, and there's at least one I haven't seen in twenty-five years.
My father, on the other hand, had only one sister who had no children. Funny how families vary.