@Balrog @DarkMahesvara @Saber @Mamako @Owl @Spingebill @Xeraser @ehhh @bleedingphoenix @skylar I've already laid out to someone else why, genetically, it doesn't make sense to reproduce with your sister
You concentrate all recessive traits whether positive or negative; see the Amish and maple syrup urine. Bottlenecks have happened many times in history and are part of why certain features are common in certain peoples.