Concept: Brass Trio who are all so territorial about each other for very different reasons.
Like, Albus and Rose are cousins who get so possessive of each other. There’s a scene in the beginning of CC where people are harassing Albus and Rose steps in front of him to get the attention, and you can interpret this a variety of ways, but imagine a Rose who’s like “step away from my cousin and bestie, he’s sensitive and doesn’t need these questions!” And That’s part of why Rose didn’t like Scorp at first because he’s stealing her best friend, and eating breakfast, lunch and dinner with her bestie. And Albus didn’t like Polly either because she was getting too close to Rose and demanding all her attention, like that’s their best friend.
Then you get Scorp, and regardless of whether you ship Scorose or Scorbus or both at the same time or neither, they are possessive. Like that is their emotional support traumatised blonde twink! Step away from their boyfriend! Albus will kill a bitch for breathing on Scorpius wrong and Rose will destroy your reputation if you so much as look at him. They will team up to protect that boy no matter the cost.
And Scorpius is also territorial about both of them but not in necessarily a jealous way, but in a protective way. He knows their families are famous and that people want to get in on that and he will stand in your way. If he suspects you don’t genuinely like Albus or Rose, he is making it everyone’s problem. They’ve been burnt before, he’s not letting it happen again.
Conversely: Steel Trio who don’t give a fuck.
You call Vincent Death-Eater-Spawn? I mean, you’re objectively wrong, but Sophia and Alice are joining in. You call Sophia one of the many slurs applicable to her? She has no reaction because Vincent and Alice call her that frequently enough that she probably thought you were them. You physically hit Alice? Vincent and Sophia will probably assume she hit you first. Especially if any of them are dating.
And then when the two trios become friends this dynamic continues of the Brass Trio being territorial and protective as fuck while the Steel Trio laugh with you.