I have a different perspective on it kind of. Because I was left alone so much and my sister was doted on - I developed much more initiative and will to learn things for myself than she did.
I was able to take care of myself when I left home young at 20. She never left home in her 20's. I was able to know what to do with a child already when I had one as I was her built in baby sitter due to the 10 year age difference.
At the time; I enjoyed that because I loved babies so we were very close when she was tiny. I'm not bitter because life's too short. Did I take the brunt of the neglect and emotional abuse - yes. Did I end up in a better position in life to empower myself though? Also a yes.
Kids who are too doted on, pampered and have excuses made for them as children, don't have the inner fire and drive that other ones do to free themselves and be who they really are when they grow up. They are more likely to follow a herd throughout life or to accept mediocrity or a job they don't really like etc.
Sometimes the older ones who are made to grow up earlier thrive better in the real world for the rest of their lives. I've seen this trend also among friends of mine who were in similar situations as myself. Of course every situation is unique -
Holding grudges or blaming our parents holds us back in life. Eventually what we do or who we become is solely on our own shoulders. If I had to choose to do it over again - I would certainly be the oldest and not the baby.