Hey @luke-pighetti,
Unfortunately, we don’t have anything like this out of the box that can be used across platform like this. It sounds like you’ve got an idea, but hopefully other developers can chime in with solutions they’ve used as well!
Hi Luke! Currently at the same stage for you. We are building an app which requires a joint membership and I am currently working through the scenarios. Hopefully answering this can provide me and hopefully you some clarity.
RevenueCat provides us with the ability to login with a userId which is the only thing we can reference. However, we are not able to check the status of other users.
For instance let’s say user-1 is not premium but we want to check if user-2 (their partner) does have premium. There is no way to do this through RevenueCat.
My idea was also to create a database collection in Firebase for active subscriptions, which works perfectly for when the user handles all interactions with in the app (sign in/up, sign out, delete account).
However, what happens when a user cancels their subscription from outside of the app and then deletes the app. How will we update the database collection? I assume RevenueCat will be updated, but there is no way to listen to this data from RevenueCat to update the database collection.
I’ll keep you updated with any progress in my thinking!
@luke-pighetti I found this reference on the RevenueCat forum. It looks like webhooks and CloudFunctions could be a neat solution to this problem 
