The Western nuclear family is a very unnatural social arrangement. Anthropologists have found that in most hunter-gatherers, the average infant is held at one point or another by 30+ people in a typical day.
The nuclear family has the twin downsides of putting tons of stress on parents of young kids, who shoulder the entire childcare burden, and deprives a lot of grandparents, aunts, cousins, and others of meaningful childcare time. In the industrialized West, for most people it's either all babies all the time, or no babies whatsoever. Both extremes are suboptimal relative to the environment humans evolved for.
The nuclear family has the twin downsides of putting tons of stress on parents of young kids, who shoulder the entire childcare burden, and deprives a lot of grandparents, aunts, cousins, and others of meaningful childcare time. In the industrialized West, for most people it's either all babies all the time, or no babies whatsoever. Both extremes are suboptimal relative to the environment humans evolved for.