Let me explain why incest is wrong. Are you familar with basic biology (meiosis, alleles, genomes, chromosomes, etc?) During meiosis, an imbreed child would be more likely to bring out reccessive traits in the chromosomes since both partners would share nearly the same genes. And those reccessive traits are at times, diseases. Of course, due to a lot of recessive characteristics becoming dominant, you get some fucked up looks too. It's about science, not morality.