Is Amir able to forgive Baba ? Is he able to forgive himself ?
These are two excellent questions stemming from the sins committed by Baba and Amir in The Kite Runner. Amir is at first disgusted with the news that Rahim Khan discloses: that Ali was sterile and that Baba is the father of Hassan; and Hassan had actually been Amir's half-brother. Amir questions his father's own dictum:
There is only one sin. And that is theft... When you tell a lie, you steal someone's right to the truth.
But Amir has come to understand his father better since their arrival in California, and the two had become close as a true father and son should. Amir's own maturity helps him to see a bigger picture, as well as the true reason for Rahim's summons:
As it turned out, Baba and I were more alike than I'd ever known. We had both betrayed the people who would have given their lives for us. And with that came this realization: that Rahim Khan had summoned me here to atone not just for my sins but for Baba's too.
In the end, Amir is able to forgive himself for his own past discretions concerning Hassan (turning a blind eye to the rape and planting the gifts to place the blame of theft upon Hassan). His own forgiveness begins through the harrowing return trip to Afghanistan to retrieve Sohrab. In the final scene, where Amir and Sohrab fly the kite together, Amir's forgiveness of himself becomes complete. Sohrab smiles for the first time,
... "Do you want me to run the kite for you?"
His Adam's apple rose and fell as he swallowed. The wind lifted his hair. I thought I saw him nod.
"For you, a thousand times over," I heard myself say.