A/B/O
Aemond has been obsessed with Lucerys since his birth. He's convinced he'll be an alpha, Lucerys an omega, and that they'll get married. Aemond shows up early; he's precocious. He's even more protective of Lucerys after that, and completely obsessed with his pretty curls and his adorable little nose.
Unfortunately, the Driftmark incident occurs, and everything changes. Well, almost everything, because in Aemond's deranged mind, he and Lucerys were married that day, they shed each other's blood, as tradition dictates. Aemond lost an eye, but he gained Vaghar, and Lucerys as his husband. Obviously, this isn't the case at all, and their family finally begins to panic at Aemond's obsession with Lucerys. The King, following Rhaenyra's pleas to protect her son, decides to betroth Lucerys to Lord Oscar Tully, an alpha male.
Aemond is furious; he and his beloved Lord Strong are already married. Why would his old fossil of a father dare defy the gods and their decrees, and furthermore, promise his omega's hand to someone else? It's ridiculous.
Years pass, and Rhaenyra and her family move to Dragonstone to protect Lucerys from Aemond's deranged mind. Aemond, for his part, refuses all marriage proposals; he already has an omega, and they are married, having shed their blood before the gods and their families. So he trains relentlessly, day and night, to become the greatest warrior in Westeros, the greatest dragon rider in history, the most powerful alpha in existence. For when his husband returns, he must prove to everyone that he alone is worthy of loving him, protecting him, and ruling Driftmark by his side.
One day, a raven arrives with great news. In fact, it might have been great news, if Alicent and Otto weren't convinced that Aemond and Vaghar would set all of Westeros ablaze upon hearing it. Lucerys had indeed presented himself as an omega, but during a visit to Riverrun, he went into heat. His marriage to Lord Tully had to be brought forward, as Lucerys and Oscar were already expecting an heir.
It took more than half of the royal guard to subdue Aemond following this announcement.