Who`s Green Lantern.. what does he do?

Like the first guy who answered said. There are many "Green Lanterns". Its a society of crime fighting people, and they have magical powers, etc..etc. The Green Lantern who joined DC Universe, otherwise known as The Justice League...is brothers with 2 other members from the "Green Lantern" society, and he kills 1 other member due to betrayal. (not in a game, on a show) and no not his brothers.