See how often they participate in the script: HERE.
Character Story: In the past, Ganondorf became a very powerful and evil ruler, using magic to control and harm others. He was banished into the Twilight Realm where he only became more powerful, waiting for his chance to escape. He holds the triforce of power.
Race Story: A race of almost all women, with one male born every hundred years. They normally live in the desert, but the Gerudos do not appear in Twilight Princess directly. Evidence of their existence still appears with crumbling buildings in the West.