Multiple domains based in same database

Hi,

I currently run a WordPress member site on a single domain. I’m trying to add a new domain that will host a few pages within the member site, but from what I’ve read, doing WP Multisite with domain masking still requires you to set up new databases, and our membership plugin does not support multi-database setups. Ideally we want members to be able to sign in on one site and still be signed in when they go to the other, and vice versa.

Does anyone know of a solution for this?

Thanks!