Child Posts

I’m trying to set-up an organization scheme that would work like this:

1. Every post can have one or more child posts.

2. Below each individual post page, there is a list of all children of that post, if there’s any.

3. In each individual post page, there are links for the parent post and for its immediate siblings, in a previous, parent, next fashion.

4. There is one aggregate archive file, where all posts are shown in an hierarchical fashion.

Is there any plugin that does that? Does anyone have any idea about how to implement this?

Rafael M.