I am not completely clear on what you are trying to do, but I would suggest having one of the instances contain another (therefore having a reference to it), or have a third instance (of a new class) contain both instances (and therefore be able to access and manipulate both of them).

Event listeners etc work well, but I prefer composition for simplicity. If only one object will be accessing a second object, there is no need to set up the whole event dispatcher thing.

Now if several objects were accessing the one object, you would have to work out a better method.