Corresponding with my brother down at East Carolina, I commented on my relationship with our stepfather (summary: Never close; sometimes antagonistic; now refuses to speak to me). My impression had always been that I had tried hard to get along with him but my overtures were rebuffed. Recently it occurred to me that my intense focus on my own wife and children was perceived as a personal affront by him. The children's families were supposed to remain under the umbrella of our parents' family. Submerged under their family would be too strong a word; even subsumed is a bit much. My independence from it was clear, even though we bent over backwards to be accommodating to family events, even when it was inconvenient.
I regarded this as individual differences in values between us, a head-butting that resulted from our individual personalities. My brother suggested that this was as much generational as individual.
Though this was a new thought to me, it rang true immediately. When I was a boy, children were considered more appendages to their parents than they are now. The mother and father were not only the authorities of the family, they in some sense were the family. I imagine this was even stronger in earlier generations, though I don't know how one would measure such a thing. Unless one was near in age to a child in another family, one pictured the family as a mother & father plus generic children. Your aunt and uncle were important, but cousins important only if they were age-mates. The authority and status within the society at large permeated even close relationships. The parents owned the family rather than merely ran it.
Caveat: I was a child then, and saw things from that perspective. Adults then might have viewed the children of other families entirely as I do now: directed but not owned by the parents. Also, any such enormous generalization has to have many exceptions to it.