The House of Dragon Credit is a Game of Throne spinoff.
House of the Dragon has a different focus. The members of a single family are vying for the Iron Throne instead of jumping from clan to clan. The potential heirs of King Viserys Targaryen are his daughter Rhaenyra and his brother Daemon.
The Hightower clan is one of the main characters in the show.
In House of the Dragon, Targaryen dreams are important.
Oldtown is where the maesters study at the Citadel. The family did not have a lot of involvement in Game ofThrones, though the daughter of Mace and Alerie was a descendant of the Hightowers. The role of queen consort was briefly held by Margaery. Tommen's mother blew up his sister, her brother and father in the Sept. explosion.
Early on in the Targaryen dynasty, the Red Keep was more active than it is today. The Hightower family became regulars at court when Aegon the Conqueror first united the seven kingdoms.
Otto Hightower is hand to King Viserys in the first episode of House of the dragon. Otto was a knight who was in charge of the Targaryen family after their son died. While building roads, sewage, and other vital infrastructure, Jaehaerys ruled over a peaceful kingdom.
It matters when the king is cut by the Iron Throne.
Viserys isn't living up to the legend of Jaeherys. Viserys values Otto's loyalty to the Targaryen family.
Like every other hand we have ever met, Otto has his own agenda. He calls Daemon unreliable and unsuitable for the Iron Throne. Daemon seems to be a bit of a psycho.
Corlys Velaryon is the Sea Snake and he tries to undermine him in a conversation. The Targaryens have a close relationship with the Velaryons. The families traced their lines back to Valyria. Both families left Valyria before the end of the world. Otto is the king's key advisor because he seized opportunities to weaken Corlys.
Otto is willing to take advantage of others. In the first episode of the show, the wife of Viserys gives birth to a son in a scene that ends in the deaths of both mother and child. Otto stepped in to help Viserys make decisions.
The house of the dragon is against all odds.
Otto might be using his daughter, Alicent, as a pawn in the game of thrones. Alicent is the best friend of Rhaenyra Targaryen. Otto implied that Alicent should try to earn the king's affections so he could become dependent on her, when he sent Alicent to Viserys' chambers. It is possible that Viserys will make Alicent queen when he remarries and tries to make another male heir.