Seriously, I'm not into incest, but the biology of human reproduction is much more complicated. For instance, having a chronic disease affects everyone's offspring, incest or not, however in the case of incest it poses a greater chance of being passed on. However, if the person is healthy it takes (scientifically) at least 4 generations for genetical disorders to form. Plus, we all need to remember that most royals tend to be step siblings or half siblings, considering how kings would have several wives/concubines. Genetical diversity is what's important for a new healthy 'unit', but it can also work the opposite way if you want to preserve a physical/mental characteristic of your offspring. Anyhow, long story short - incest is bad, but it's not as bad as people think. Educate yourself. 😂