So, you are simply taking issue with nuclear families being the norm (mom and dad with kids, instead of mom, dad, grandma, etc and kids)?
This seems not to be very germane to the issue at hand, which would be non biological parents raising kids in unusual combos, such as 2 dads, a mother and 2 dads, etc. Nuclear families are certain a much more modern construct, but then again so is living in single family homes and driving cars. Not sure why you bring it up.
“It's usually seen only in advanced civilizations and not always there.”
You (or your professors) are confusing the NUCLEAR family's fairly recent appearance with all family (marriage/blood-related) forms.
The extended family (father, mother, children, Grandparents, uncles and aunts) is indeed ancient, extending at least as far back as the beginning of recorded history. All members of extended families reared their offspring; specific roles were varied by ability, wealth, etc. The records are clear and extant, to say otherwise is pure BS. You can find some exceptions among primitive African tribes, but to extrapolate their exception back onto the rest of humanity is absurd, (and academically dishonest).
Brytlea and FrogJerk: This guy is spouting pure BS as taught by many in the academic world today. His cited reference “The Origins of War in Child Abuse and The Emotional Life of Nations” should be a big hint as to the inanity of his argument! This cr@p was starting to be taught when I was in school (I didn't fall asleep in my classes, LOL!), but most of us had taken other courses (such as ancient history) that we could effectively challenge these anti-western bozo professors.