The favorite story of Amir and Hassan when they are young is "Rostam and Sohrab", from the Shahnamah, an epic of ancient Persia. It is the tale of the great warrior Rostam, who mortally wounds his nemesis Sohrab, only to discover that Sohrab is his long-lost son. Hassan loves the story because its tragedy touches his heart, and he ofter cries when Amir reads it. Amir, on the other hand, likes the story for a selfish reason. He plays a trick on the unsuspecting Hassan one day by making up his own version of the tale, and Hassan likes it so much that Amir is encouraged to write a story of his own. Amir discovers his lifelong talent and passion for writing because of Hassan's genuine appreciation for the story he so treacherously fabricates.
On a conscious level, Hassan names his son after the story's hero Sohrab because he loves the story so much and remembers it many years later when his child is born, but on a metaphorical level the tragedy of Rostam and Sohrab mirrors his own life. Hassan never knows that Baba is his true father, and is never able to experience the love that they might have shared, just like Sohrab does not discover his own father until it is too late (Chapters 3 and 16).
Also in the tale of Rostam and Sohrab, Rostam deceives Sohrab by telling him that he must throw his enemy to the ground three times. Similarly, Amir deceives Hassan with the incorrect story.
While Rostam is the primary hero of the "Shahnameh", as Amir is in "The Kite Runner", Sohrab is the martyr of the story and the character for the which an audience weeps; just as Hassan is.