I think there's an underlying cognitive dissonance between parent/child node relationships in digital tree data structures, and parent/child human relationships in biological family tree structures.

People and animals typically have two parents, while nodes typically only have one parent!

Would a more humanistic collection API support both "mother" and "father" relations, instead of just a single "parent"? Or should they be even more inclusive, and support any combination or number of "mother" and "father" relations, and even user defined parental relations?

I'm joking, but maybe it would be a good addition to Brainfuck.