Are all orphans or children of single parents unbalanced? I can't put much credit to that claim. The same with children of same sex couples.

Uncommon life and family arrangements have existed since humans are humans. That is why all societies have edicts on what "normal" relations are and why deviations from the norm have been so persecuted throughout history.

Yet...

China has an ethnic group where one woman has several husbands. The children stay with the mother, while the men have the role of providing for the household. Suffice to say it is hard to know which man conceived which child, so they are colectively considered fathers to all children.

In Africa and the Arabian peninsula it is common fare for one man to have several wives and where there is that tradition all women are addressed as mother by all children.

Again in Africa, there is a tribe where children are raised, from very young age, by their uncles and aunts, away from the parents.

The first time I read about it, what came to mind was two brothers or sisters exchanging children, like a sort of perverse hostage situation: "you raise mine, I raise yours, nobody kills the other!"

Yes, I have a strange mind.

Divorced couples. Remade families. Same sex couples. Adoptive parents and foster families. Non standard families, whatever that may mean. And then we have the "really" out there arrangements, like poliamory. How about nudists? Or hippies?

So what?

Growing up, there was this family in my street that was composed of two couples, where each woman had given birth to a child of each man. The four lived as a small community, where all children address both men as father and all women as mother.

None of them grew up "fucked up". Or did, only just as much as anyone else.

No.