I recently came across this site, which tries to explain how your birth order can affect your character.
Birth Order
I was the first born of two sons. I was also the first born in a generation, and was the first grandchild for all my grandparents, as well as the first child born amongst my parent's contemporaries.
My brother was born when I was two years and three days old. I remember being introduced to him at Bramley Meade, and being told he'd brought a Golliwog for me, as some sort of compensation. I remember liking the Golliwog, but thought it was a poor swap for not being an only child anymore.
I also remember offering to feed him his pureed baby mush, and whilst my Mother wasn't looking, scoffing the lot, thinking he might then waste away! Forty odd years later, I've resolved these issues, and love my brother dearly.
Some of the characteristics listed on the site, I might admit to, but certainly not to always thinking I'm right!!!

So, what about you?
Do you think your birth position has affected you?
Are you a seventy year old baby?
Do you still feel neglected?
Does it matter?