In a translation of "Rostam and Sohrab" by Helem Zimmern (see link below), the story begins:
"Give ear unto the combat of Sohrab against Rostam, though it be a tale replete with tears."
From the beginning, the reader knows that this Persian legend will involve not only tragedy ("tears") but also some type of conflict between the two characters. Thus, throughout the tale, the father-son pair, Rostam and Sohrab, are separated. Sohrab spends his whole youth searching for his warrior father but begins to lose hope that he will ever find him. Ironically (as many legends go), Rostam and Sohrab meet in battle against each other, and even when there is opportunity for them to know each other's identity, they are deceived by manipulative villains or ruled by their own skepticism. It is not until Rostam throws Sohrab on the ground, breaking his back, that he and Sohrab realize that they are father and son. While Rostam is able to spare his son torture from Sohrab's enemies, he must still live with the knowledge that he delivered the death blow to his only son who wanted nothing more than to know his father.
The story also possesses Aristotle's elements of tragedy. It includes a tragic hero (both Rostam and Sohrab) whose tragic flaw (primarily pride) leads to his (in this case, "their") tragic downfall.
As a side note, Khaled Hosseini masterfully uses "Rostam and Sohrab" as an allegory in his bestselling novel The Kite Runner.