Your grace, you cannot wed your own sister, the faith forbid incest; “One god made us all, Andals and Valyrians and First Men, but he did not make us all alike. He made the lion and the aurochs as well, both noble beasts, but certain gifts he gave to one and not the other, and the lion cannot live as an aurochs, nor an aurochs as a lion. For you to bed your sister would be a grievous sin, ser…but you are not the blood of the dragon, no more than I am. What they do is what they have always done, and it is not for us to judge them.”; Doctrine of Exceptionalism