James: It is very obvious when he is jealous and he tends to make it known by keeping you closer to him and being over the top with affection so others know you are together.

Sirius: He would get annoyed and sulky if he notices someone is being flirty with you. Along with this, he would nudge you until you focus on him and he make sure that you know he is there.

Remus: He would be even quieter when he is jealous and glare at the person who is causing him to be jealous, especially if it is close to the full moon. He might even slip his hand into yours because he feels insecure.

Peter: He doesn't let anyone see that he is jealous and it often turns into him leaving you alone because he feels that you deserve someone more confident and secure than he is. Occasionally he will glare at the person if he cannot find a way to escape from the situation.

Regulus: He would tense up and probably tell the person to back off because he feels threatened. He would then kiss you and tell you how much you mean to him.

Lily: She would go quiet, watching you carefully while trying to pretend that is isn't jealous. Eventually, she would try to get your attention but asking you about homework or something to do with school.

Marlene: She would also be quite obvious, showing even more affection to you and becoming clingy so you pay attention to her. Her main move was to hug you from behind and glare at the person who is making her feel jealous.