I read the book and I know that Daemon supposedly cheats on Rhaenyra with Mysaria (and possibly Nettles, depending on whose account you believe). According to the accounts, Rhaenyra is perfectly fine with the infidelity with Mysaria (although not with Nettles, who may be Daemon's lover, bastard daughter or protegee).
He was unfaithful to his third wife, Rhaenyra Targaryen, taking Mysaria and possibly Nettles as his lovers. Daemon made many friends in King's Landing, especially in Flea Bottom, and among the gold cloaks, as well as in Pentos. However, he was intensely disliked by Ser Otto Hightower.
Mysaria became Daemon's mistress of whisperers at some point. After the fall of King's Landing to Rhaenyra, Mysaria served as the queen's mistress of whisperers in all but name, although she did not join the small council. Rhaenyra apparently approved of Daemon sleeping with Mysaria each night.
2 episode of House of the Dragon, Rhaenyra (Emma D'Arcy) and Daemon (Matt Smith) stopped fighting their feelings for one another and finally got together. However, this was more than just an illicit liaison, as Rhaenyra and Daemon got married at the end of the episode.
Fire & Blood also suggests that Daemon has an affair with House of the Dragon's future character Nettles, a 17-year-old bastard girl who claims the dragon Sheepstealer for the Blacks.
Daemon stumbles back to the Red Keep and is brought before the king, who confronts him with the White Worm's intel. Daemon, pointedly, doesn't deny that he and Rhaenyra had sex.
While House Of The Dragon episode 4 showed Daemon was able to seduce Rhaenyra by kissing and undressing her, he couldn't fulfill the act due to impotence.
Turns out, Rhaenyra and Daemon are endgame, meaning they have a sexually tense relationship, eventually hook up, and get married—which is pretty significant from a power play perspective considering (1) they both want the throne and (2) their Targaryen union is almost sure to guarantee that happens—even though Alicent ...
After Daemon's first wife dies, he gets together with Laena Velaryon—who was initially suggested as a bride for King Viserys. They have two daughters. Meanwhile, Rhaenyra marries Laena's brother, Laenor Velaryon, and they have several kids.
It was abundantly clear in the season finale that Daemon truly values Rhaenyra as the queen, and it doesn't appear to be for his own gain. All of his actions indicate that he looks to her as his leader even before she's taken power and has every intention to get her to her rightful throne.
Daemon chokes Rhaenyra because he's angry, because he feels she's making the wrong decision, and probably even because she reminds him of his late brother.
We last saw her find out the truth in "We Light the Way" that Rhaenyra lost her virginity to Ser Criston Cole (Fabien Frankel).
We know that while the two came close, they never actually did the deed. Daemon, thrown off by his lack of ability to shock Rhaenyra, left her to get drunk and pass out. While Rhaenyra did go on to sleep with Criston Cole — the big problem of the episode — Viserys (Paddy Considine) was made more cautious of Daemon.
Her next child whom she's now pregnant with, however, will be a different story. In House of the Dragon episode 8, Rhaenyra Targaryen is pregnant with her daughter Visenya. Despite Rhaenyra and Daemon's excitement over having another child, their daughter will tragically never take a breath of air.
Joffrey Baratheon spoils Rhaenyra Targaryen's fate on Game of Thrones. As Joffrey tells us, eventually, Rhaenyra's half-brother Aegon Targaryen will feed her to his dragon Sunfyre. She dies as her son, Aegon III, watches. That's the bullet point version.
In the fourth episode of "House of the Dragon," the pair kiss in a brothel, and when rumors that they were intimate together reach the king, Daemon tries to get Viserys to let him marry his niece Rhaenyra. The king refuses, but their story doesn't end there, because by episode eight, they're married.
In George R.R. Martin's book Fire & Blood, we are told of the incident where Rhaenyra Targaryen's husband Laenor Velaryon dies while attending a fair in Spicetown, on the island of Driftmark. We learn he was “stabbed to death” by a knight in his father's service, his paramour Ser Qarl Quarry.
As the two dragons struggled in the Battle Above the Gods Eye, Daemon plunged from Caraxes, wielding his sword Dark Sister and stabbing it into Aemond's remaining eye. Both dragons crashed into the Gods Eye, and Vhagar drowned with Aemond's body still chained to the saddle while Caraxes died on the shore.
Back in her chambers, Rhaenyra's gaze lands on the handsome Ser Criston Cole (Fabien Frankel). After some initial reluctance by Criston, who has much more on the line as a lowborn member of the Kingsguard, Rhaenyra playfully seduces her long-standing crush and they have sex.
Daemon and Rhaenyra share two children together: Aegon III and Viserys II.
Aegon III, aka Aegon the Younger: Rhaenyra and Daemon's first child together. Aegon Targaryen, aka Jon Snow: Yes, he comes much later, when a song of ice and fire plays out. But he could be the prince that was promised, though that's still up for debate.
According to the accounts of Septon Eustace, prior to her turning sixteen, Rhaenyra lost her virginity to her uncle, Prince Daemon, after he seduced her.
While Daemon and Rhaenyra have been circling each other for quite some time, the finale revealed a darker and more toxic aspect of their relationship when, arguing over how to proceed against Aegon II (Tom Glynn-Carney), Daemon chokes Rhaenyra in order to get his point across.
Daemon grabs Rhaenyra by the neck, choking her and saying that Viserys wanted desperately to make his reign more significant. He says dreams didn't make them kings, dragons did. Rhaenyra realizes that Viserys never told his brother about the prophecy.
Later, in episode seven, Daemon tells Rhaenyra that he and Laena were "happy enough" in their marriage. In that regard, there was far more love between Daemon and Laena than there ever was between him and Rhea, even if it wasn't entirely romantic.