My dad was born in 1925. He lived with his parents and sisters and didn't share a household with grandparents aunts or uncles. My mom was born in a small town in Italy on the eve of WWII and orphaned when she was ten. Again, there were no grandparents aunts or uncles, or friends or neighbors living in the same household, and none were in the picture to care for her. She was went to boarding schools until she could emigrate to America, where her uncles lived. During school breaks she lived with neighbors in her home town.

I don't know enough about my grandparents to be able to answer, but I think it's likely that small three-generation households were common somewhat common, i.e. a grandparent and one of their children, that child's spouse and that set of grand children. But I think multi-family households and intentional household relationships not bound by marriage or parent/child bonds were rare in their day as well, at least in the US and western Europe.