Answer:
It is up for debate who is to blame for Suhrab's passing. We can hold Rustam accountable for not recognising his kid and for refusing to hear Suhrab's cries for mercy because he was too arrogant. On the other side, Tahmineh, Suhrab's mother, is also somewhat to blame for withholding Suhrab's identity from Rustam prior to the conflict.
Dramatic irony is a literary trope used in stories when the audience is aware of information that the characters in the story are not. The characters in "Shahnameh" are unaware of Suhrab's true identity or his connection to Rustam until it is too late; nevertheless, the viewer is aware of both. This irony adds to the story's tragic aspect by generating suspense and emotional impact.