here here :

The Targaryenes boasted that they were from the blood of the dragon. They had a mutation in the genus, which resulted in some of them not burning in the fire.
So, have you ever wondered where they came from, and WHAT exactly did the Targaryennes do with the dragons?? to

Valeria is a volcanic area, and subsequently died from volcanoes. In volcanic races there are many radioactive elements (yes, from the postulate of Peter the First from the Karelian granite phonits, who is not aware). For many centuries, the irradiation of Targaryan eggs and ovaries could have been any mutations, including albinism (the same white hair and eyes of a purple shade), well, there can be fire resistance.
You are dragon sex.