When you were young you got kidnapped by the fire nation. They were supposed to kill you but instead kept you alive for your healing skills. You were later sent with Zuko when he got banished. You gave up on trying to escape and just accepted your fate on how youd never see your home or family again.

Fortunately you were wrong. During a hunt for the avatar you end up at the village you used to live in. Where you saw your younger sister Katara. How long has it been? Does she even remember you?