People say that birth order has a lot to do with personality. Firstborns are used to and demand a lot of attention. Middle children constantly seek approval because, well, they're stuck in the middle!
The babies of the family are often the most independent. To this theory, I'd like to add that the sex of your siblings might be just as impactful.
Growing up with my older brother helped to shape me as a person. There were, of course, the stereotypical lessons; it's because of him I learned to love football and appreciate the comedy masterpiece that is the movie Step Brothers.
But more importantly, I learned to understand the ways in which boys and girls are truly different (and exactly the same). To generalize, boys are uncomplicated but they are not unemotional.
Just because men don't express themselves as openly as women, does not mean they're any less sensitive. On the other hand, I also learned that boys, like my brother, aren't afraid to be wrong, to look silly or to be judged - and that this is something girls could learn from. By watching my brother I saw that gossip and drama are just not that interesting; but laughter, fun, and simple things can make your day.
This works both ways of course. I know I've had a hand in making my brother the sweet guy he is today (his current girlfriend can thank me later). He'd be the first one to tell you how much he respects and admires women. He understands that women are just as competitive and capable as men and I think that comes from growing up with me.
It occurs to me that growing up I never once wished that I had a sister instead of a brother. Thinking about it, I'm sure it would have been amazing to have a sister to share things with. It certainly could have improved my beauty skills! (I never could french braid hair and to this day I can't keep nail polish unchipped for more than an hour.) But for me, I'll take a brother any day.
When you grow up with a sibling of the opposite sex you understand that whether you're male, female or anywhere in-between - we're all just humans who make each other better by understanding the other.
