Like Baba and Ali before him, Amir could never bring himself to call Hassan his friend nor accept him as an equal. Although
... Ali and Baba grew up together as childhood playmates... in none of his stories did Baba ever refer to Ali as his friend. (Chapter Four)
It was the same with Amir and Hassan. Ali and Hassan worked for Baba and, in Amir's mind, he could not be true friends with a mere servant. In addition to their lowly Hazara heritage, both Ali and Hassan exhibited physical deformities--Ali's crippled leg and Hassan's harelip--that both amused and embarrassed Amir; additionally, Hassan's mother was a local prostitute who left Ali shortly after Hassan's birth. Amir's jealousy over the attentions shown by Baba toward Hassan was overwhelming, and Amir was willing to lose Hassan's companionship entirely if it meant that Baba would pay more attention to him. Amir was able to give Hassan "a friendly shove" on occasion and even profess that
"You're a prince, Hassan... and I love you." (Chapter Four)
But Amir was a cowardly elitist, and he could never profess his true friendship for the boy who ran his kites and defended him whenever necessary. After all, Hassan
... was just a Hazara, wasn't he? (Chapter Four)
As was mentioned in the previous post, Ali and his son, Hassan, were servants in Baba's home. Ali and Hassan were both Hazaras, an ethnic minority of Shia Muslims who live in the majority Sunni country of Afghanistan. Hazaras were persecuted and discriminated against in Amir's hometown of Kabul and were considered second-class citizens. Amir, an elite Pashtun who comes from a wealthy family, believes Hassan is beneath him because of Hassan's ethnicity. Despite the fact that Amir and Hassan are very close and play together nearly every day, Amir is conscious of the social class system. It would be considered taboo for a Pashtun to have a close relationship with a Hazara. In addition to the social taboo, Amir is extremely jealous of Hassan. Hassan is able to win Baba's affection when Amir cannot. Amir's jealously and willingness to appease his father overpower his feelings of friendship with Hassan, and Amir attempts to sabotage him.