Parallel Worlds and Alternative Universes?

I was at a gathering a few weeks back hosted by one of my sometime collaborators. We've known each other for seven years or so, and have worked together in various ways - writing, editing, or co-directing projects.  As it turned out, one of his friends, by pure chance, has a connection with me that goes back decades.

At one of my friend's larger gatherings, one of his friends came up to me and asked me if I'd grown up in New Hyde Park, on Long Island, and went to Wickshire School.   I answered yes to every one of his questions, but strange as it may seem, it wasn't anyone I knew directly - but very likely, someone who lived a life parallel to mine as we were growing up.  A year younger, he lived probably 20 houses down the block and around the corner in my old neighborhood in New York.  We knew some of the same people - he even remembered Julie, our legendary ice cream man - and the nice guy who polished floors all over the neighborhood - we all knew when we were very young.  

We went to the same elementary school - but when you're a young kid, sometimes kids that are even a year younger than you are kids with whom you generally wouldn't waste time.  So, we lived lives that were very close - we probably sat near each other on the school bus, and we apparently shared some of the same teachers - but we never knew each other.  Nevertheless - we shared an experience - we shared a place, and we shared a time. We just operated in slightly different dimensions.