Org-brain allows me to have more than one parent. For example, I have a list of books I've read and reviewed (for personal use). When I started using org-brain I added author entries as parents; for comics I can do author and artists. So in the tree it looks like

* Read Books

-- Book Title

   Review

* Authors

-- Author Name

-- Author Name 2

* Artists

-- Artist Name

But in org-brain I can connect all of these in a logical way so I can jump through it quickly.