I have developed multiple car communities of 20 different brands on 20 different domains. So that they can get popular faster in S/E and in people's mind. Which they did. They all are running with PHPBB-SEO so all pages are in html and google loves them all.
Then i linked all into one mother company website and created a one page website to redirect traffic to their own specific brands and started branding that one website.
Now my 20 individual sites are famous but mother company isnt. So my thinking is to merge all 20 website into one mother company like domain.com/car names and then switch off there PHPBBSEO to not to generate HTML pages in mother company domain name. And leave those html optimized 20 domains also running as it is.
My question is: will this also cause as a duplication of content in google and other search engine eyes?