WordPress: How to make a subsubdirectory

If I’m understanding your question correctly, as long as you’re okay with them all using the same theme (it gets much more complicated if you want them to look different), but you should be able to export the posts from the other two blogs and import them into the one you’re keeping.

Then create a “top” page for each purpose and set the posts from the imported blogs under that top page via the Parent function.

The end result would be one site with three distinct areas controlled by the taxonomy.

This does not work if you need to use separate themes, however.