When We Were Young

So my best friend's sister got married. Why is that a big deal? Because this chick has been all over the sexual, wild child spectrum in her 30 years. She was a part of a snotty clique in high school and came home the summer after her sophomore year of college declaring she was a lesbian. That Christmas she brought home her "girlfriend", who just happened to be one of her best friends from high school who we also did not know was a "lesbian". Turns out, that whole lesbian thing didn't take and a few years ago she started dating a dude. They've been on and off and on again and off again ever since, from what I hear. Obviously my best friend and I get along fantastically, but my relationship with her sister has been...complicated. We've never been friends, yet we've known each other our entire lives. Since their mom passed away last year we've talked more but it's still just a 'whenever we're in the same place' kinda small talk. We don't actively seek to keep in touch. That said, she's still family and knows she can call on me for whatever she needs and the reverse is also likely true.
You know how some siblings are very similar, while others are polar opposites? That's the case with the best friend and her sister. They're each other's only siblings but were raised by a small village of aunts and uncles and with their cousins, so it was all just one big mob. They have never had a close, sisterly bond; the best friend has that with my sister and her own sister has that with a cousin. But they get along much better now than they did growing up, they used to fight constantly. In a way, the best friend is her fathers' daughter in that she's very warm and spiritual and fun. Her sister is more like their mom; quiet and reflective and with the occasional mean streak. The difference between her and her mother is that the latter would only show that mean streak when she was upset. Her daughter used to be such a mean girl in her teenager years but she seems to be mellowing out now. Their dynamic makes me not want another daughter for fear that my girls would have similar opposite personalities. (But who are we kidding? We all know I still want another one.)
I am...baffled. By the marriage, by the lesbian-ness and then non-lesbian-ness. It's also interesting what kind of feelings sneak up on you when your younger siblings do something before you. The natural assumption is that you'll do things in a certain order because...that's just how it should be. I remember being totally thrown by my brother having kids before me (I wasn't so torn up about him being the first to get hitched since neither the sister or I wanted that). Yet when my sister had her daughter a few years prior, there was no such feeling since she's older than me (if only by two minutes, I still consider her my older sister). My 29-year-old cousin is considering marrying his girlfriend before the end of the year and that has me feeling similarly to when my brother had a kid before me. As does this spur of the moment marriage. When the hell did I get so old? Further adding to my old man-ness today is that my "teenager" is 22 and entering her senior year of college. She'll graduate college next year. I still remember when I graduated college. Seriously, when did I get so damn old? Fortunately, I am not alone in asking such a question since the best friend is equally puzzled over her sister's wedding. I tried to make her feel better by saying technically she was the first to get married...and divorced. Shockingly, that did not go over well and she pointed out that I have a kid in college and one entering pre-school (she knows I be illin' over that). *sigh* Old age sucks.