Ethan:
This guy is usually a gentle giant in terms of everything else. But when he's jealous, he doesn't even have to say anything you just feel it. Maybe even a "Back off." In a slight growl Is all you'll get from him, but he really doesn't need much to be intimidating. Usually his gaze and demeanor is so nice and calming, it just makes his more rash emotions even scarier.
Lawrence:
Dude. Guys insane. You already know I'm gonna say this guy will kill anyone you looks in your direction.
Eugene:
He would probably get really quiet and stew in his emotions. He is a really insecure boi and not really confrontational. So as soon as you two are alone he asks for validation and that your not going to leave him. He's a validation seeking boi and thankfully your a patience validation giving person, so he always feels secure in the relationship. Probably very touchy and want to be close/cuddle with you.
Zion:
Dude literally just not give a fuck. If he sees anything that makes him jealous, he'll make it apparent to everyone that your his. Like aggressive kisses in the middle of what your saying, maybe putting his arm around you and making snarky comments about whoever your talking to like "Wow this guy talks a big talk, maybe he's compensating for something." Stuff like that. His lack of fucks really just stems from his confidence.
Harry:
He isn't the confrontational type much either, but maybe while your talking he'll intertwine his fingers with yours or just make his appearance known in general. Usually your probably oblivious to the fact the person your talking to is flirting to you, or vice versa. But he trusts you, so these little things like holding your hand is just a reassurance to him. After your probably apologize about the whole thing and he's forgive you in a heartbeat, he just loves being around you and he wouldn't trade it for the world.