[alephnerd]

Depends on how old you are.

If you're in your 20s-30s, best case your grandparents grew up in the 1950s-60s - which absolutely wasn't a walk in the park, but the average American was miles away the richest person on the planet back then, and the "nuclear" family was the structure of choice (that's why it's called the nuclear family - 1950s techno-optimism a la Fallout)

On the other hand, if your family immigrated then the familial ties based system continued to exist.

[Michelangelo11]

Err ... no ... the "nuclear" part comes from "nucleus", in the general sense, and the expression long predates nuclear technology.

https://en.m.wikipedia.org/wiki/Nuclear_family