what is revealed about Amir and Hassan's relationship

Kite fighting brings Amir closer not only to Hassan but to Baba. It is the only sport at which he is proficient, which matters greatly to strong, athletic Baba. Amir admits, "Baba and I lived in the same house, but in different spheres of existence. Kites were the one paper-thin slice of intersection between those spheres." Amir feels so neglected by Baba that his longing for Baba's love and respect lead him to betray Hassan not once, but twice. Amir's victory brings him closer to Baba than ever before, a fact that Hassan's rape would have overshadowed; because of this, Amir does not stand up for Hassan or tell anyone about the rape. Later on, when his guilt becomes unbearable, Amir prefers to drive Hassan and Ali out of the house rather than admit to what happened and risk losing Baba's affection.