According to Targaryen family customs, Viserys, like his sister Daenerys Targaryen, was born from the intermarriage between “Mad King” and Queen Leila.
Both brothers and sisters inherited the Valyrian national characteristics of Targaryen, with silver hair and purple eyes.
In order to regain the Iron Throne, he betrayed his only sister to the Dothraki Khal Drogo in exchange for %100,000 of his cavalry.
But deep down, he had extreme disdain for the Dothraki people, a steppe people, and regarded them as barbarians.