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

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.