There are indeed parallel existences in our world. There are people who exist on Earth that in effect, don't exist to me outside of a concept. For example, Kazakhstan (which I had to Google to spell correctly) is very much a real country with real people leading very, very real lives.
However, to me, they exist outside my own reality. They are only real to me as a concept of "Kazakhstani people" which is an empty concept as I know nothing of their culture or even exactly where they are (I will learn as soon as I finish typing this).
The point is, that they exist in a parallel reality to mine. To them, I am not real, and neither is my life. Our lives evolve simultaneously, and to some degree I am sure affect each other, yet our realities are not the same.
A concept of something, or someone, it's not the thing or person itself.