So word has it every person on earth has at least once close look-alike walking around somewhere.
…Yeah, no shit. It’s kind of obvious, actually. Like, think about it for a second. New people are being born every second. And what with such a large diversity in the global gene pool, the looks of that person can be defined as random. After some time, there’s bound to be a very similar strand of DNA in a newborn child as one in a baby that’s a year old or so.
If you didn’t quite follow that, think of it this way. I have an endless deck of cards. If I keep pulling cards out of it, surely I’ll get two Jacks in a row eventually. The same thing’s with people, except the possible kinds of “cards” you can pull is much, much larger.
From a smaller scale we jump to an immensely big one. Planet. Look up at the sky at night. See al those stars? They’re suns, and have planets orbiting around them. Some have very few, while others have tens of planets orbiting them. It’s very well possible there’s already a planet out there with the exact same buildup as earth. Hell, keep going far enough, and you may just find an exact copy, with you and me and everyone in it!
Ah, the fun of infinite possibilities in an infinite pool of results.