Okay, so you've got one world. Then you've got other versions of that same world, and sometimes different versions of the same people crop up on different worlds. I've met several other mes, and in reality, I'm an alternate universe duplicate of a guy named Cable. Sort of. ...It's kind of complicated.
Huh. Okay, that's new. I'm thinking maybe we're not different versions of each other.
Multiversal dynamics. It'll make your head hurt until it doesn't.
Maybe, maybe not. Different worlds can sometimes be really, really similar, but other times can be pretty different. Names, places, people, they can all be similar or really different.