How to read/write to a Meteor app's mongodb from another Meteor app?

I would like to have one Parent Meteor app which holds user’s info about its Children meteor apps each one of which hold their own data. Is there a way Parent and Children can communicate with each other to read/write data from their respective mongodbs?
Basically, I would want the user management to happen at Parent after which it re-directs the user to whichever Child sent the request for user authentication etc and then the user carry on their operation with the local mongodb of Child. How can I achieve this in practice. Any help is highly appreciated