I must say that the dream concept has crossed my mind as well but I'm not going to eloborate on that because it cannot be proven in any way.
Here's a thought: Maybe the people of Termina originate from the same genes as the ones in Hyrule. Maybe, when the goddesess created the world they gave both worlds the same gene pools. This way there could be similarities between the worlds and they could still evolve to become slightly different. Well, that's just me using fanfic to explain myself
Not a good habit.