Why would anyone think that in an alternate reality there would be another version of yourself? That thought would suggest that every parent, grandparent, and so on in your lineage married or at least had a child with the exact same person as they did in this reality.
Well if that were the case then what the hell is so alternate about that reality? The odds against something like that happening seem astronomically small. So I really don't know why TV shows and movies always portray alternate reality's as having exactly the same people but with different personality's. Come on SYFY writers think outside the box.