Basically tidus is the copy.Tidus is a Dream of the Fayth, created by the Fayth to facilitate the ultimate destruction of Sin. Tidus's existence is a product of the Fayth's dreaming of Tidus, a way to manifest a physical form for him in the world of Spira. Tidus was inspired by Shuyin from FFX-2, reflecting the Fayth's memories of the real Zanarkand.