See saying that doesn't help "what if it is". Currently the probability that it exists is extremely against your odds. Read this
I believe there is a way humans can share dreams through an unknown part of the brain, it extremely hard to detect or prove and exists in another dimension
This may sound unusual but that is what a hell of a load of people believe. The only way to prove this is by taking it logically step by step. Even If we were having shared dreams without realizing it, it wouldn't make a difference. Currently its about establishing it validity.