Interesting thought, maybe the same effect still occurs though but more on a community basis. Historically the nuclear family doesn't make much sense so perhaps these different personality traits would occur regardless but just be based on the people in your town/community around you instead
Discussion
"Historically the nuclear family doesn't make much"
This is modern revision. the nuclear family has always been the fundamental unit of society. If social memory was reset to 0, the nuclear family would reemerge as the first social structure within 9 months.
Tribal structures would reemerge in 30 years as nuclear families add a generation. The fact that Dunbar's number is only 150 indicates that once the founding couple of a nuclear family dies, the clan fractures.
Yes there is shared responsibility in small groups, but never to the point where no one knows which child is whose or where they sleep at night. the nuclear family remains as the child's immediate hierarchy and link to the tribe.
Good point, I hadn't thought of that. Thanks!