Birth order and why I like what I like

I was talking to a friend this morning who I joke with that our brains are twins because we tend to think about and react to things in a pretty similar way.  He and I both happen to be the oldest child in our families, and we both tend to like guys younger than us. His therapist suggested to him that the reason he likes younger guys is because of social constructs -- he was raised to fill the role of the man, and generally in male-female relationships the male is older.  I hadn't reallly thought about that before, but I took it a step further -- I wondered how being the oldest child in the family contributes to that.  In my family I was raised to be a role model and example to the younger children, and I didn't have any older siblings to look up to.  I also had the responsibility to look out for them and take care of them.  Maybe this causes me to naturally gravitate toward younger guys and want to be in the role of mentor and caretaker. I've always thought it was more because of low self esteem, though -- I relate more to younger guys because I lack confidence around people my age or older. I think I tend to act younger also.  Anyway, my friend mentioned that that could be true (that as the oldest child we gravitate toward younger guys) and that most of the guys he has liked have also been the youngest in their families.  And it surprised me to realize that that was true for me too.  My first crush was an only child, my first and only and very brief boyfriend was an only child, my second crush is the youngest in his family, and the guys I'm kind of interested in right now are also the youngest in their families.  Many of my gay friends are also the youngest.  Why is that?? Research has shown that there is a higher likelihood for a person to be gay for every older brother that he has.  So is it just that there are alot more gay people that are the youngest in their families? Or do me and my friend go for younger guys because that's what we are socialized to do? And now my sociologist mind is thinking even more...I wonder, since me and my friend both beat the odds and were born gay without having older brothers, would that affect how "gay" we are on the Kinsey scale? Are we "more gay" than a gay man with 7 older brothers? Hehehe...just things to think about. Comment and let me know what you think. Time to go clean the kitchen :)