Evaluating Ghost - possible to mix Ghost and Grav?

I am evaluating Ghost. My project uses Grav flat file CMS and particularly the Learn2 theme.

I am wondering if it is possible to combine Ghost and Grav, where Ghost’s membership and paid subscription feature is used to guard access to Grav content on the same server?

If it is possible, how is it done, and could it be done in Ghost Pro or will I have to host my own Ghost stack?