We're starting from two different situations. The main one: I know I should be using pages instead of posts for building my structure, but all the data comes from a site build in java and totally customized.
So there are some posts that are the main one in a series, then there are other posts that have the title as a tag (mixed with other tags). There is a 'main' category and 'chapter' category with no parent/child relationship (Should be a relationship between those two?).
I want to show those 'child' posts that have the title of the main post in their tag list, and, when I enter in a 'child post' I need the 'parent' one to be listed next to the others. It's a little tricky.
Are there any ideas? By know, I get the normal 'related posts', via tags. I need something more 'exact'. :(