There's no concrete evidence taht I know of, but you might like looking into the work of Stephen Laberge; he's a researcher with a primary focus in lucid dreams. Some of Laberge's books talk about situations where close people like married couples would report similar dreams upon awakening in a laboratory setting.

I don't remember the specific tribes, but in the early 1900s there were reports of westerners coming back from visiting tribes in Africa that reported entire peoples who would all go to bed and reportedly hold meetings together within their dreams. The possibilities seem interesting.