Combining HTML homepage with internal pages that are on 2 separate WordPress'

Ok, so I feel like this can’t be that hard to figure out. It’s a law firm website that was recently converted from HTML to WordPress. The developer split up the two law practice areas – criminal defense and family law – into different WordPress’ and left the homepage in HTML. Needless to say, this is a huge pain. I need to combine everything into 1 WordPress.

Can someone explain how I do this? Almost everything is the same between the two 2 WordPress installs – CCS and plugins.

Details I’m most concerned about:
– Homepage for Criminal-side WordPress is /criminal-defense/
– Homepage for Family-side WordPress is /family-law/
– What all is included in the imported content when you use the WordPress import/export