As a child, Sora's only known family was his father Kazuma, who he looked up to greatly and wanted to follow in his footsteps, later believing him to have been killed. After his father's presumed death, Sora went to live with the monks of the Fire Temple. At the temple, Sora trained hard in hopes of some day avenging his father and clearing his name, as Sora refused to believe what a horrible man people claimed him to be.

(Source: Naruto.wikia)