Of cause your parents matter emotionally provided they took care of you. But I did not grow up with them and my two years younger brother as only points of reference. There where so many other people I could learn about human mental variation from. I expect other people to have a comparable social experience. At least if they grew up in a modern, Western society. Or any society where you can learn to know your fellow beings.
We had relatives outside my nuclear family which I met regularly. In addition, there were my parent’s families and these friends’ families. I also grew up in an area of apartment buildings. So there were plenty of neighbours easy to get to. I was also allowed to move freely within built-up areas from at least the age of seven. It was not exactly like my parents watched like hawks over me.
When I was one year old I go my first family care. This was not a special solution but was offered by the City of Stockholm in the 80ies. I later got another family care who also looked after my brother. From the age of five I went to nursery school in the mornings. However, this was education through play and not conventional classroom education. I don’t think children are mature enough for that until the age of seven to eight.
From the age of seven I went to what I see as a proper school. This was the normal age to start school in the 80ies. Before the year you turned seven there was no compulsory school attendance. We even had acclimatization in school to teach us what conventional classroom education meant. I don’t think all the children have had child care before starting school. But the very most of them probably had.
How normal was my upbringing? I think it was rather normal at least until about the age of twelve. My family travelled around in our motorhome for a few weeks each summer. However, I could only talk with Norwegians, Danes and some Finnish people, these are culturally rather similar to us. So I don’t think the travels have affected me much. At least not in terms of understanding different cultures.
How about people who only ever gets home schooled? These would still have relatives, neighbours and/or their parent’s friends. They then inevitably come into contact with some degree of individual variation. Their circle of aquatints does not absolutely have to be representative. However, it always shows a considerable part of existing variation. Please note that one comes into contact with it before learning to read and write. We don’t have five-year-olds isolating themselves on Internet forums. Especially not in English which is particularly hard to learn to read and write.
But if you grew up in a dangerous cult? Then you did not grow up as part of a wider society. Such an upbringing in a cult also have its own problems. If one manages to leave the cult one would still be maladjusted due to unnatural upbringing conditions. Such people don’t become preachers or professional writers.
If one spend almost one’s entire upbringing on a lone farm, miles from its closest neighbour? Then one has not grown up as part of a society at all. I would expect such a person to be crudely misanthropist. This in contrast with behaving as if one was used to a position in society which did not exist in one’s lifetime. Without a circle of aquatints there would have been no signals of such a position.