I’ve just started the second season, and it’s interesting how Lucerys’s death came about at Aemond’s hands and what led to it. I haven't read the books, so I won't talk about them, instead, I'll talk about the series and only the series.
That said, it is interesting to note that Lucerys's death was, in a way, almost an accident, in the sense that Aemond had no real intention of killing him.
This brings to mind their childhood, as the real rift between Rhaenyra’s children and Alicent’s children stemmed not from their own actions toward one another, but from the consequences of the disagreements among the adults around them. This led to the fight in which Aemond lost his eye, ultimately fostering a unique and deep-seated resentment in the dynamic between them.
Naturally, Aemond would resent the fact that Lucerys went unpunished for it, after all, his and Aegon’s position as the king’s sons always seemed precarious due to the perception Alicent instilled in them and the very "favoritism" (for lack of a better term, given that Viserys was hardly kind or fair to them either) he showed toward his first family.
And naturally, Lucerys would defend the honor of Rhaenyra and his siblings against the constant insinuations regarding their parentage and the risk that such talk could undermine the fragile protection afforded by their positions. For although they held titles and were heirs to respected seats of power, all of that could be lost at any moment if the whispers of bastardy were repeated often enough to transform rumor into fact.
So, in a way, even the specific conflict between Lucerys and Aemond ends up being more of a reflection of the conflicts among the people around them than of the boys themselves. This is interesting because is implied that, despite everything, they actually got along relatively well during their childhood. They used to play, tease each other, and train together, but after the major conflict that drew them deep into their respective families' feuds (Aemond losing his eye) that bond was buried beneath what they had to do to maintain their positions of power.
So, Lucerys’s death is an accident in the sense that Aemond was reenacting the old dynamics between them, however, since they are now caught up in the conflicts of their respective families, replicating that dynamic inevitably leads to tragedy. Aemond had no intention of killing Lucerys (he only meant to intimidate him) but given the looming war, they could no longer engage in the childhood antics that once defined their relationship, and the outcome was bound to be violent regardless of the intention.
So yes, Lucerys's death is a tragedy, but the real culprit is the cycle of violence that began long before them, and I find that truly sad and interesting to witness.
