Cassidy learned a long time ago that everyone in the world was out to take care of only themselves. No one
really cared about anyone else. Everyone was selfish...so Cassidy adapted. Whether he wanted to be or not, he had to look out for himself and himself only, because no one else was going to. It was a fact that he initially grieved being forced to admit, but when his magic finally manifested, things changed.
Soon after learning about his magic, Cassidy began to close himself off to others. He'd always been a quirky, quiet kid, but now he was actively choosing to isolate himself. He was intelligent, perhaps too intelligent for his own good, and knew that his presence often made others uncomfortable; he'd heard people say that they felt something sinister around him, something that made them feel like their blood had frozen and their bones had shattered. He'd never understood why till he'd learned of his magic, and had always done his best to be as good of a kid as possible to make others wish to be around him in spite of the terrible feeling they experienced, but once he knew why, he didn't see much point in continuing the charade.
Instead, he began to pour his time into learning his craft. Cassidy throws himself into the things he likes to do, often neglecting to care for himself due to his intense focus on a goal, and his magic is no different. He'd spend hours pouring over books to learn as much as he could about magic in general, scouring the castle library for anything and everything that could help him learn while also trying to avoid suspicion. He got surprisingly good at lying, though it helped that no one had any reason to suspect him of having ulterior motives; after all, why would a kid who'd been good for such a long time suddenly be up to no good? Besides, it wasn't like Cassidy was doing anything wrong (besides putting his mother at risk for being exposed as having had an affair), and he made a point to never lie. Instead, Cassidy would simply twist the truth.
At first, he did so for necessity, but as he experimented with his magic, Cassidy realized that he had a knack for twisting words. Soon, it became a game of seeing just what he could get away with saying, while all the while never technically lying to anyone. It got old soon enough, but it taught Cassidy what he needed to know. When he needs to, Cassidy can turn on the charm and charisma, using anything and everything to his advantage.
Still, the more easily manipulated those around him were, the more Cassidy began to isolate himself. He grew colder, more distant, especially after he stopped playing his game of manipulation. If he was being honest with himself, he was tired. Tired of people being stupid. Tired of hiding what he was. Tired of keeping secrets. He didn't do anything about that tiredness though. Instead, Cassidy just grew jaded towards others, becoming more irritable as the days went by. Soon, it was bad enough that his parents caught on, but Charming and Cinderella had no idea what to do with their son that they no longer recognized. They tried to get through to him, but Cassidy was untouched by their attempts to break through to him.
So they sent him away.
At boarding school, Cassidy had no pretense to keep, no facade of who he'd been before. No one knew anything besides the fact that he was the son of Cinderella and Charming, and it was freeing. Cassidy was able to be grumpy and jaded without anyone thinking that he was suddenly, radically different. Instead, the other students were initially shocked that a prince could be so jaded and harsh, but quickly grew to just understand that that was who he was. Not many tried to do anything to get to know him, instead just staying out of his way for fear of angering the brooding boy whose initial bullies quickly proved to be an example of what would happen if you messed with him; no one knew what exactly happened, but after messing with Cassidy, each bully had something terrible happen to him. That quickly made most steer clear of the prince, which was what he wanted. Though he still kept his magic a secret, feeling some sense of fidelity to his mother and not wishing to see her exposed and punished for her crimes (and not wishing to hurt his father figure, Charming, by revealing the truth of his mother's deception), Cassidy didn't mind. It was something he didn't want to share anyways; his magic was his, something no one else knew about, and something about having it as his secret made it special and precious. It worked out well.
The few that did press through Cassidy's cold exterior, however, quickly found a boy who was ultimately quite clueless in interacting with others. The prince had never had a proper friendship, and so became so standoffish because he did not want to risk being hated. He has a severe lack of trust for others, but also has a deep seated wish to be accepted that he has repressed to a point where he barely even realizes it is there, since he is seemingly doing everything in his power to be rejected and isolated. He often says exactly what he is feeling as bluntly as possible to those he's close too, and does not often outwardly show many emotions besides irritation. He is working on being a bit more delicate in his presentation, depending on what he is going to say, if it's someone he actually cares about that he is speaking to. He also has proven himself to be quite good at reading other people's emotions, and is fairly decent at reading others' motivations, though his pessimistic view of what motivates others tends to skew things so that he only sees the negative ulterior motives. Still, Cassidy ultimately is an awkward boy who sees the world in a poor light due to circumstance and so has tried to close himself off to others. And if you can make it through his tough, outer shell, you'll find a fiercely loyal, honest friend who will protect you by whatever means necessary, one who is intelligent and stubborn and grumpy and motivated and an absolute mess to deal with, but a good friend nonetheless.