Hello, It is known that the Targaryens have a history of mental illness - one of the symptoms of lead poisoning - and it is not know why they are like this. The Targaryens practiced incest but after generations of offspring produced this way, there would be a lot more problems apparent so I don't think incest made them "mad." Enter in the lead poisoning theory. Scholars speculate that the Roman Empire fell because its people - mainly the aristocrats and the imperial family - were exposed t