It is normal, GRRM did not invent Incest.
Strip out all the nudity and sex and all you have left is violence and torture. That’s okay right? And GRRM must have secret desires to kill and torture people because he wrote about it once.
I’ve heard the argument that the GoT universe is similar to Middle Earth. Ridiculous. GoT is godless, cruel, and nowhere I’d like to live. Good and evil are relative. In Middle Earth good and evil are clearly defined. There’s a God that’s supposed to be the same as the Biblical one, though he rarely shows up. The civilized people have respect for one another. I don’t think the movie did enough justice to the book, but maybe it’s the same with GoT. I didn’t read it.