So, in my various family systems (mom + older sis, mom + partner + partner's kids, mom + partner), I am either the baby, the functional oldest, or the only.  So I often have a hard time picking out where I am in the birth order scheme.  I do tend to fall more in the 'youngest' category, and I was definitely more spoiled than my older sister was.  Mom was REALLY strict with her, and only MOSTLY strict with me.  

Yet, I'm also the functional oldest if you count my family with my mom and her partner, as my bio sister was basically in college by that time.  My first stepsister is actually a few months older than me, but was a grade behind in school so I definitely was "older" in a lot of ways that don't involve having children (she got pregnant at 17).  My second stepsister is 2 years younger.  Our moms often felt they had to make an example of me, or hold me up as the child exemplar that the others should emulate, which didn't always work well.  In that way, I kind of identify as an oldest, but this is definitely the weakest of my birth order associations.

AND, of the four of us 'kids,' I am also definitely the only one who "belongs" to both my moms.  I mean, we all belong to each other, but I was the one who lived with them the longest and was really "raised" by both of them.  So I often identify as an only, too - and boy did they spoil me as an only!

I think we've all mostly gotten over it by now.  We're all functional adults, at least, 2 of us with advanced degrees, one of us with kids, three of us in long-term, stable relationships, and all of us with steady (if not always well-paying) employment.  But yes, the birth order stuff does continue to rear its ugly head with us from time to time!