At the end of the fourth episode of House of the Dragon, King Viserys is about as angry as we’ve ever seen him. His daughter and heir, Rhaenyra, stands accused of being intimate with his brother — her uncle — Daemon. They may not have consummated the deed, but they certainly almost did, and Rhaenyra, at least, was super into it. Viserys is eager to accept the fiction that nothing happened between his daughter and brother, but he’s also quick to force the former into a political marriage with her cousin and banish the latter. It is a testament to how messed up the Game of Thrones universe is that a viewer could be forgiven for wondering what the problem is here. A niece and nephew having sex? What’s the big deal, Viserys? I thought incest was cool in Westeros.
Incest has been a fundamental part of Game of Thrones since the very beginning, as the series premiere ended with the shocking reveal that twins Jaime and Cersei were fucking, and the show ended with Jon Snow hooking up with Danerys Targaryen, his aunt. Incest is so common in this franchise that it’s sometimes hard to parse when, exactly, it’s supposed to be a bad thing. It’s shockingly easy to just accept incest in GoT and, by extension, HotD. Viserys probably accepted it, too, suggesting his revulsion at Rhaenyra’s alleged affair with Daemon does not stem from the fact that they were closely related. To understand where Viserys is coming from, it’s helpful to review when incest is or is not taboo in Westeros, going back to George R.R. Martin’s original writing for guidance.
As documented across the pages of The World of Ice and Fire and Fire & Blood, supplementary books in the Song of Ice and Fire series that detail the history of the fictional world, incest in Westeros is not acceptable with one exception: the Targaryens. Prior to the arrival of the dragonriders, roughly a century before the events of House of the Dragon, pretty much everybody considered incest to be a sin. Followers of the Seven certainly found it abhorrent, as did those who worshiped the old gods. Even the Wildlings were opposed to incest. Carnal relations between parents and children or between siblings were forbidden. Relations between an uncle and a niece were similarly frowned upon, though at least one Stark married his half-niece without any fuss. (Marriage between first cousins, it should be noted, was and is totally cool according to Westeros tradition. It’s only when more intimate familial relationships become … intimate relationships that it’s a problem.)
This widespread anti-incest stance was the norm before the Targaryens arrived and it continued through their reign and well after it. In Game of Thrones, which takes place around 200 years after House of the Dragon, Jaime tries to murder a child rather than let the truth of his relationship with his twin sister become public knowledge, and Craster, the Wildling with a habit of marrying his own daughters, is a pariah among the Wildlings. Westeros culture is and always has been firmly against incest. But the Targaryens didn’t come from Westeros.
In Valyria, the mystic lands in Essos where the Targaryens originated, it was customary for dragonlords to wed brother and sister. The closer the relationship, the better, as these arrangements kept the dragon-riding bloodlines pure and controlled. Aegon the Conqueror was married to both of his sisters, Visenya and Rhaenys. When his conquest was finished and he was anointed king of the Seven Kingdoms, nobody objected to his polyamorous, incestual marriages. The High Septon and the people of Westeros might not have liked it, but what were they supposed to do? This guy and his sister-brides and their dragons just took over the entire continent.
However, when Aegon’s heir Aneys took the throne and attempted to marry his brother Maegor to his daughter Rhaena (Maegor’s niece), the High Septon objected, and Maegor was instead married to the High Septon’s niece, only for Maegor to eventually take a secret second wife, which pissed off the faith. The faith was further incensed when Aenys did eventually marry Rhaena to her brother, his son and heir Aegon. Aenys was named King Abomination, and there was a massive outcry across the land that only got more intense once Aenys died and Maegor took the throne. Maegor the Cruel, as he was known, was perhaps the worst king in Westeros’s history, and he engaged in a brutal war with the Faith Militant over many issues, including the Smallfolk’s objection to the Targaryens’ incestual behavior.
His successor, Jaehaerys the Conciliator, was able to repair the relationship between the crown and the faith, as his name suggests. Part of that was the establishment of the Doctrine of Exceptionalism, a new, official tenet of the Faith of the Seven that codified incest as a sin. However, because the Targaryens came not from Andalos, where the Faith of the Seven had its roots, but from Valyria, they were exempt. The dragonriders were simply not like other men. Incest was — and, at the time of House of the Dragon, is — officially okay for Targaryens and only Targaryens.
So what this all means is that Viserys, Jaehaerys’s grandson and heir, likely wasn’t so upset about Rhaenyra and Daemon because of their close blood relation. Under the Doctrine of Exceptionalism, such a marriage between Targaryens would be acceptable in Westeros. However, “marriage” is the operative word there. It would still be a huge scandal if Rhaenyra slept with Daemon outside the bonds of marriage — especially because her eventual spouse has huge political implications and because Daemon has a history of coveting his brother’s throne. It would have been an even bigger scandal if Rhaenyra became pregnant as a result of such a tryst.
So Viserys may have been a little disturbed by the idea of his teenage daughter sleeping with his adult brother (although he himself married Alicent when she was a teen), but the strength of his reaction almost certainly had less to do with incest and more with politics. Classic Game of Thrones.