We don't know how many parallel universes there are. All we know is that, in this one, she watches him from afar with his wife and children. But what if there was another universe where she didn't have to watch and wait for him? What if it was all possible in this universe?

Meredith and Derek knew each other when they were kids... watch them grow up together and possibly drift apart.

MerDer is already married before they go to Seattle [this us the continuation of Bright and Shiny]