I'm bugged by the trope In Spite of a Nail when applied to Alternate Universe or time travel. Alternate words that have a large divergence (Nazis Won Earth, etc. ), but alternate versions of the main character still exist. If the world is that different I'm doubting your parents still met under the same circumstances, if at all. I always find it disturbing when the heroes go to another dimension/universe/timeline/whatever and entirely screw it over in order to save their home-reality.