In a single family, you have parents and toddlers. Coercion and hierarchy are there for education.

What we are talking here is a community of adult people.

Children becoming fully independent from the authority of their parents and relatives at a certain age is a uniquely modern, American idea. Everywhere else, and throughout the rest of human history, hierarchies of age and blood relation tend to be immutable and pervasive.

Parenting doesn't have to be hierarchical. Giving support doesn't constitute hierarchy is the sense that anarchists use the term.