I'm getting increasingly irritated by fics that have Charles react to feeling jealous of Edwin's love interest with indiscriminate, open hostility and rudeness tbh???
It's like people saw Charles' reaction to the cat king in canon and assumed that was his whole personality without taking into account the fact that by the end of their first encounter The Cat King:
Forced him & his friends to go to the old cannery
Greeted them with not one, but TWO very obvious threat displays (hundreds of individuals who can hurt the boys + a blatant implication that the Cat King had people killed before)
Took Edwin away without consent, for a long period of time, and without guarantee he'd bring him back
Trapped them all in Port Townsend despite Edwin making it clear it wasn't safe for them to be there
Did or said something to Edwin that left him rattled and acting uncharacteristically tense*
Meanwhile, Charles was polite to Monty from the get go, did not react to Monty's initial rudeness beyond checking that it wasn't his fault, insisted on taking Monty's case when Edwin tried not to, and didn't outwardly show any bitterness when he tried to broach the subject of what he clearly thought was Edwin's budding crush on Monty. In fact, when he thought Edwin was going to admit to it, he smiled and joked about Edwin wanting to look nice for his crush
Like yes, we the viewers could tell that he wasn't happy about the development, but he was never rude, possessive or aggressive about Monty until his betrayal was revealed, and the fact that the first behavior is what stuck in people's minds frustrates me a lot if I'm going to be honest
* I can't remember of the top of my head if TCK say anything obviously sexual in the first conversation so I'm not counting it here, but his behavior was clearly predatory, it's no wonder it rang alarm bells in Charles' head even BEFORE you take all of Charles' other issues into account