Laravel - Multi domain using single login server?

I'm setting up around 4 Laravel 5.3 based apps at the moment, they are all part of one "ecosystem".

I would like to use a main central site that holds all the user accounts (login.site.com or similar). I may also use these user details inside mobile apps in the future so I assume i'll need some sort of JWT based system.

I've thought about using Laravel Passport to achieve this but I don't think this will work for this scenario - the users will login via a web app AND eventually a mobile app. Passport is just for API authentication I believe.

All my other sites will be on different servers so I can't share the database unfortunately, and I am very stuck and confused on how to go about this idea properly.

Thanks in advance for any info on this, just to clarify that I am not asking you to code the whole thing for me, simply to help point me in the right direction on how to do this properly.

via Chebli Mohamed