Aemond and Daemon Targaryen have a lot in common – they ride two of the most fearsome dragons in Westeros, they have excellent hair, and they're also both pretty fixated on each other.
It's Daemon's intention to get revenge on Aemond – at Rhaenyra's request, after the death of her son Lucerys in the season 1 finale – that leads to the horrific events of Blood and Cheese. Aemond was the target of the murder plot, though it was young Jaehaerys who ended up gruesomely losing his head (and whether Daemon gave the order for that particular killing is left deliberately ambiguous).
