Warning: contains SPOILERS for House of the Dragon!
The success of Dune franchise, which could include its own incest plot line. House of the Dragon's most prominent incestuous relationship is between Rhaenyra (Emma D'Arcy) and Daemon Targaryen (Matt Smith), an uncle-niece married couple in pursuit of the Iron Throne. In Dune, psychically-linked fraternal twins Leto II and Ghanima marry each other to help fulfill a prophecy known as the "Golden Path," which promises to save humanity from extinction. The Golden Path is introduced in Children of Dune, the third installment of the Dune series.
Both House of the Dragon and Dune are adapted from fantastical book franchises with a powerful legacy and target very similar audience demographics. Therefore, House of the Dragon could indicate how audiences react to the controversial topics that the Dune franchise could cover. That said, Dune's second part that's releasing in 2023 and its potential third part will still only cover the rest of Dune and all of Dune: Messiah. Whether the modern-day Dune franchise will even cover Children of Dune and therefore its incestuous plot is still up for speculation. Still, House of the Dragon is a promising litmus test for the potential success of a more extensive Dune franchise going forward.
Why Daemon & Rhaenyra's Relationship Didn't Hurt HOTD (Despite Everything)
The marriage between Rhaenyra and Daemon Targaryen is clearly unhealthy, yet this works in House of the Dragon's favor. One of the show's strengths is the way that it creates a cast of flawed, complex characters that don't fit squarely in either a good or evil category. This factor helps to properly frame its incestuous relationships as inherently abusive, despite them being established as a Game of Thrones Targaryen marital tradition. Adding to the abusive nature of Daemon and Rhaenyra's marriage are its grooming aspects established early in House of the Dragon and Daemon's upsetting choking scene in the season 1 finale.
Still, their incestuous marriage isn't taboo for the sake of taboo. Looking at it simply, it helps display what these characters perceive to be an exercise of power: Rhaenyra believes she's choosing to marry Daemon out of love despite being groomed by him, and Daemon marries Rhaenyra to get closer to the Iron Throne despite knowing how contentious her succession is. It also shows the power of marriage in Westeros. Houses and alliances become stronger through marriage, yet by following a Targaryen tradition and marrying each other, Daemon and Rhaenyra blatantly contain their House's power. While it may seem that Game of Thrones makes this Westerosi element more accepting, this isn't the show's message. Incest is used as a vehicle for complex character development, which ends up strengthening House of the Dragon.
Dune's Incest Plot Is Less Weird Than HOTD's (But Still Very Weird)
Dune's incest plot will be comparatively less controversial than any of House of the Dragon's instances of it while retaining its own weird elements. Leto II and Ghanima are the highly prescient children of Paul Atreides and his beloved Fremen concubine Chani. Children of Dune establishes that the Golden Path prophecy requires Leto II and Ghanima to keep the Atreides name in power. They marry in name alone but don't produce any heirs. Instead, Ghanima carries the Atreides name through her children with Farad'n Corrino. Still, this plot is dependent on Dune 3's production and the growing Dune franchise.