Has your view on nature versus nurture shifted since having kids? I've heard some people start to shift very heavily towards viewing people's personalities as part of their nature from birth after raising children of their own.
I've actually gone all the way to the other side. I see in my kids all the issues they've inherited from me and their mother, plus all the extra they get from a different environment from the ones we grew up in. I see where they diverge in attitudes, of course, but that has very clearly a lot to do with firstborn vs sibling and (increasingly, with age) their sex, rather than anything incredibly unique or innate.
Before I had kids, I always assumed that babies were like undifferentiated blank slates and that they grew unique personalities over time and through experiences.
If anything, it's the exact opposite. My kids and the kids of my friends pop out of the womb with insanely huge personality variation. You don't see it at first because babies have so few visible outputs. But once they hit toddler age where they can walk and talk and do stuff, you realize each one is a complete batshit crazy wildcard.
It's only through years of socialization that they learn to mold their inner oddball into something stable and functional enough to participate in society.