The Gan Jin tribe had been in conflict with the Zhang tribe since approximately 0 ASC. Tribe lore held that while their founder, Jin Wei, was carrying a sacred crystal orb necessary for the tribe's ancient redemption ritual, he was attacked by Wei Jin, founder of the Zhang, who stole the orb.
Years after the incident, the tribe was attacked by the Fire Nation, eventually forcing them to reside elsewhere. They set a course for Ba Sing Se, but needed to pass through the Great Divide. During the journey, the Gan Jin were forced to travel alongside the Zhang tribe, who were also en route to Ba Sing Se. The tribes traveled in separate groups in an attempt to prevent conflict. AvatarAang and his friends escorted the two groups across the canyon, and Aang was able to settle the dispute between the two tribes by revealing to them that Wei Jin did not steal the orb from Jin Wei but rather scooped up a fumbled ball in a game called "Redemption". In addition, he stated that the Sacred Orb was simply a ball, and the Great Eastern and Western Gates involved in the ritual were just the goal posts in the game. However, unknown to either tribe, it was simply an elaborate ruse constructed by Aang to bring peace.
Members of the Gan Jin were more civilized and cultured than the Zhang. Similarly, they were much more tradition-bound, and tended to be precise with their way of living. The Gan Jin adorned themselves with white and gold robes, and condemned uncleanliness. They tended to be arrogant and snobby, paying more attention to minor details and being inflexible in their way of living. Despite their culture, they seemed to be fairly amiable with outsiders, observed when they socialized with Katara relatively easily.