Baba and Ali: Foil characters

"But mostly because Ali was immune to the insults of his assailants; he had found his joy, his antidote, the moment Sanaubar had given birth to Hassan." pg 10
I found it interesting that when Ali and Hassan leave Baba says that Ali was like the brother he never had. This close bond surprised me. They were complete opposites. The above passage shows this. Hassan is Ali's whole world however Amir has to really try to get Baba's attention and love. Another way they are different is their religious beliefs. Ali has memorized the Koran while Baba denies that God exists. Also their life styles are very different. Baba is rich and comfortable while Ali is a poor servant. These two different men may be opposites but the things they have been through together formed an unbreakable bond between them.