While I’m curious about those statistics as well we could take a step back and think about the fact that the typical nuclear family of the USA is atypical historically and in much of the world today. Children used to be raised by basically anyone close to them. The “village” so to speak would raise the child.
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I believe most studies that focus on child-rearing overwhelmingly notice that a child with multiple role models/guides is far more likely to have a balanced healthy mental outlook than one raised by a few. In other words, two moms will raise a healthier child than one parent. I am not sure if it would be healthier than a mom and a dad, but I am willing to bet those nuances are so slight it is not worth consideration since economics, culture, and environment probably out weight them meaningfully.