You might be able to rig up something using Thingworx on the Experience Server to manage the shared state information. For example, the "master" experience could have script code that triggers a Thingworx event or property change when the master clicks a "play" button, and the "child" experiences could have listeners that check for the event or property change and execute a parallel "play" action to keep in sync with the master.
It would require a bit of programming and some Thingworx configuration to track all the important aspects of experience state that should be shared across users.
If you need to have multiple groups viewing experiences at the same time (possibly), then that further complicates things. You would need a more complex data model in Thingworx to keep track of separate states for different "sessions" or "groups", and forming a synchronized group would need some way of identifying which viewers should be synced together.
