✮ ⋆ ˚｡𓅨⋆｡°✩

First, to make sure we’re all on the same page in regard to the terminology I’ve used: AKOTSK generally does not state the characters’ ages and so this analysis concerns book canon, in which Aerion was indeed a child himself when he threatened Egg with castration (Daeron is eighteen in “The Hedge Knight” making Aerion seventeen at the oldest, and Egg is eight or nine and says it happened when he himself “was little,” meaning—from his young perspective—quite a few years prior). In such scenarios the question of where the child perpetrator got the idea in the first place inevitably arises, and in this case it’s quite possible that simply growing up in a violent feudal society in which castration is a legal punishment and child marriage is not uncommon was sufficient; however, some individuals have unsurprisingly learned from their own experiences of CSA.

Then there are other details to consider. Aerion’s privileged status as a prince certainly played a role in making him who he is, as did the Targaryen tradition of close kin marriage, Maekar’s parenting (more on this later) and Aerion’s “madness”…but the dangerously “mad” Targs have generally also experienced at least one specific adverse life event as an inciting incident. Viserys III (an obvious narrative parallel to Aerion) and his father Aerys seemingly had some difficult personality traits to begin with, but at about age thirteen Viserys became homeless and the sole guardian of his little sister after Willem Darry’s death (Dany also says that “When Viserys sold their mother’s crown, the last joy had gone from him, leaving only rage”) and Brienne’s maester probably correctly opines that the six months of captivity during the Defiance of Duskendale “had driven King Aerys mad” (Varys also did all he could to stoke Aerys’s paranoia). Another potential example is Maegor, in whose case quite a few environmental factors were at play—even in addition to the possibility that Visenya had used blood magic to conceive him in an attempt to produce an heir who would be strong and ruthless in response to Aenys’s “weak” disposition and regression after his own mother’s death—and it’s particularly of note to me that he was married off at only thirteen to a twenty-three-year-old and that this union was immediately consummated. GRRM has written a number of characters subjected to early sexual experiences—or sexual abuse in general—who go on to behave in ways quite evidently informed by this; Aegon IV was known as Aegon the Unworthy due in part to the broad consensus that his promiscuity was unacceptably excessive, and—while this pattern of behavior was once again the product of no single factor—I do not think it is a coincidence that when he was fourteen the twenty-four-year-old Falena Stokeworth “made him a man.”

In regard to your second question—“who are the most likely perpetrators”—personally I do not have anyone specific in mind, but if it were a man around Maekar’s age this might explain some of the strangeness inherent to his relationship with Aerion. By which I mean, given Maekar’s personality and drives (e.g., prideful, desires to escape “the shadow of his eldest brother”) it’s not at all surprising that he casts Aerion in the role of the golden child in contrast to Daeron, but Aerion’s matching investment in behaving as the perfect son around Maekar and absolutely no one else (in the novella, unlike the show, “all smiles and chivalry so long as his father is watching” proves an accurate description of Aerion’s behavior) is otherwise a bit harder to fathom. It’s not solely a means of staying out of trouble, as he doesn’t bother with the act in front of Baelor, the second-most powerful person in the realm: even before Aerion proceeds to kill Humfrey H.’s horse we see him take “a pause to dip his lance to Prince Baelor, a pause so brief that it was almost perfunctory.” Aerion reminds me a bit of Saera, whose “sisters all misliked her to various degrees,” who ended up in Lys after a scandal around the same age as he did, and whose relationship with her father bears a slight degree of similarity to Aerion’s with Maekar:

[L]ong before she was half-grown, Saera had learned the art of getting anything she wanted from her father: a kitten, a hound, a pony, a hawk, a horse (Jaehaerys did draw a firm line at the elephant).

As for the matter of these puppeteers, by the time Aerion is done twisting the tale it will be high treason. The dragon is the sigil of the royal House. To portray one being slain, sawdust blood spilling from its neck . . . well, it was doubtless innocent, but it was far from wise. Aerion calls it a veiled attack on House Targaryen, an incitement to revolt. Maekar will likely agree. My brother has a prickly nature, and he has placed all his best hopes on Aerion, since Daeron has been such a grave disappointment to him.

While I find the relationship between Saera and Jaehaerys much more suspect (the reading that she experienced CSA at his hands is supported by quite a volume of evidence, whereas I’m personally less inclined to think that GRRM intended the same when it comes to Aerion and Maekar), Aerion’s willingness to please Maekar and him alone still suggests a level of enmeshment to me. This could be a matter of poor parenting and nothing else, but—as I mentioned above—GRRM’s precedent of writing characters whose interpersonal relationships are patterned somewhat on their past experiences of sexual abuse forms an additional line of inquiry here.

Finally, I think this part was originally @aerionbrightflame’s idea, but the following is worth examining more closely:

He thinks he’s a dragon in human form, you know. That’s why he was so wroth at that puppet show.

Considering that Aerion ultimately dies in an attempt to become a literal dragon, this belief of his seemingly operates somewhere in the realm of wish fulfillment. A “madness” brought on by an experience of powerlessness, perhaps, in view of the relative physical vulnerability of dragons and humans*…which may shed some further light on his extreme reaction to the puppet show’s outcome. On that note, I want to reiterate that this reading is not an attempt to downplay his treatment of Tanselle and Egg; personally I just find it more rewarding to speculate further on causality as opposed to attributing his actions to privilege and Targaryen marriage tradition alone (plenty of other Targaryen men constitute counterpoints) or, worse, simply concluding that he’s “inherently a bad person” (not really GRRM’s style).