I'm going to start this out by saying I'm an open-minded skeptic. I believe there's a possibility for things like shared dreaming to happen... but have never seen a convincing case.

Anyways, I arrived at an interesting conclusion using some logical points I've heard before on the subject.

The brain gives off certain wavelengths of energy. Different frequencies of vibrations can both affect the brain and be given off by the brain. Theoretically, people will share dreams/thoughts being on this same wavelength (or, depending on belief of the "energy body" or similar concept, might still have to resonate similarly).

So, then, if two people are trying to share dreams/thoughts/etc., wouldn't it make sense for people to synchronize these? Now, I don't have nearly enough of a detailed knowledge to know that it would even change the resonance of each person's thought patterns... however, two people who are close to each other may try centering around the same frequency for a while either before or during sleep. For example, they may find a highly resonant crystal and find a manner of striking it, or else both use the same binaural beats. If we accept the things mentioned above, shouldn't this also theoretically increase the chance of sharing things?

Not to say I'm even entirely convinced, I just thought maybe it should be considered.