Yep, we can see a lot of people here have had little experience in raising children. Some will just seem to naturally say "I accept that", and another kid that will be like "f you, I don't do what you tell me" born a year apart and raised in the same household. Nurture can moderate these behaviors, but nature is strong.

I was more referring to the children that compare themselves to other children, or differences between what they have/are allowed to do and what others can.

It's why I prefaced it with "It can".

Every child is different, but a big impact is every parent who has or hasn't dealt with the normal childhood stuff every parent can have, plus the extra, or latent reactivity can be modelled and passed on.