What it means being the oldest child

I do not really know what I need to be writing about therefore for the next few hours or days I will be trying out some topics that I'm interested in writing about.
First and foremost. I'm a mom of two. A son I had the pains of labor for and my niece I gained custody of when she was an infant herself. Now I've gone through all the trials and tribulations of caring for my niece full time and since shew as a wee little thing. But as truly being a first time parent it seems to me that I've grown accustom to the things that happen and should be happening for the child. So much so that it seems as if the thrill is gone. Many people would know what I'm referring to when I talk about the thrill of parenthood. All the First! But with me there is no surprise. I've been seasoned. My partner feels that my son is being robbed of the title of being the first. I can understand that to a certain degree. He's the first Grandboy on both sides of his family. But my question is: Is missing out on the first really all that important? My niece is three years older than my son. I've been through everything with her and nothing has changed with birth of my son other than the introduction of sibling jealousy.
For me, I was the oldest of 4. I hated it. I had to share everything and there was nothing I could call my own because I had to share. My partner on the other hand is the oldest of 2. He didn't have the same problems as me and I could list the grand differences of why we both had such difference in relating to my son and niece should be treated. The most striking part is that my parents are divorced and life growing up was very hard( this will be in a later post) but his life on the had has two parents celebrating over twenty years of marriage. I'm sure there were bumps along the way but they are a thriving companionship.
I honestly don't think that my son will be missing anything if he lacks the title of being the oldest child in this household. As far as I'm concerned I plan to make sure that things are equal between the two even though I know this will present me with many obstacles ahead. Right now I know that things can be shared and that there are certain things that must be different and we will tackle these differences as they present themselves. Just because my niece is the oldest does not mean that I will make her do more than her share of what is expected from her. My niece reserves the right being the first born girl and my son the right to being the first born boy. So they both are first and they both are the oldest. I will be learning a lot from this situation as I continue to perfect my parenting skills.