Unfortunately, watching House of the Dragon requires preparing your mind for a lot of incest. Whether it’s siblings forced to marry one other by their parents or a star-crossed romance between uncle and niece… It will happen, and it will happen frequently. What’s the deal with all the incest on House of the Dragon? Why is House Targaryen so self-absorbed? The insane Targaryen practice of incest is not without reason. Although it may not make sense to us, it does to them.
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Why is House Targaryen so incestuous in House of the Dragon?
According to George R.R. Martin’s books, House Targaryen’s habit of incest dates back to their Valyrian beginnings, where the practice was more frequent and accepted. The belief is that by avoiding outsiders, they may keep their bloodlines “clean,” keeping both their social standing and their dragon-riding powers.
Their “ideal” weddings involve siblings. But in other situations, the marriages may involve uncles and nieces or aunts and nephews. Targaryen cousins may also marry on occasion, as is the case across Westeros, where even first cousins may marry without raising serious questions. Some Targaryens, such as Princess Rhaenys, marry members of other noble houses for political, religious, or romantic reasons.
So, is it acceptable in the Westeros?
Actually, it’s not! After King Aegon I conquered Westeros, the first marriage between the Targaryen brothers sparked the first uprising against the kingdom. The Faith of the Seven is the dominant religion in Westeros. Yet, certain areas, such as the North, continue to worship the old gods. And according to the Faith of the Seven, incest between siblings and between parent and child is considered an abomination.
Remember that time on Game of Thrones in season 5 when Cersei pushed for a militant sect of the religion of Westeros to take control, and that bit her in the back? She was then accused of sleeping with her brother and made to walk around naked as everyone chanted SHAME, SHAME, SHAME! That is the Faith of the Seven, which is prevalent in Westeros during the House of the Dragon.
What happened was that King Jaehaerys, who ruled before Rhaenyra’s father Viserys, petitioned the Faith leadership for an exception for his family. Simply put, everyone except House Targaryen considers incest to be a sin and an abomination in Westeros. They are literally exempt from the rule.
There was a lot of drama surrounding House Targaryen’s rampant incest before Jaehaerys received the Faith’s blessing. In fact, there was an uprising led by the Faith Militant that reappeared in Game of Thrones season 5. Cersei should have remembered that tidbit, but she probably thought she could get an exception for herself as well.
While the Targaryens’ incestuous practices may appear as “strange customs” to the rest of Westeros, devotees of the Faith of the Seven have no reason, or at least no grounds, to turn on the rulers because they prefer marrying their own. Sure, but  George R.R. Martin covered all of his bases in explaining why the Targaryen incest goes uncontested in House of the Dragon, whereas the Lannister incest helped break the realm apart in Game of Thrones.
