Through chapter 5, 6 and 7, I think the realationship between amir and hassan is only master and servant.
According to these three chapters we can simply find out that hassan is so loyal to amir he regards amir as his brothers and even can fight for him, but amir just think hassan as his servent. Now let's how hassan loyal to amir. At other child's home, hassan protected amir from others, he encouraged amie to fly the kite in the morning, helped amir to running the kite, playing poker card and loss in purpose, understanding amir even amir shouting at him, gived amir courage before the match. And in page 54, "eat dirt if i told you," "If you told, I would." from these things we can see how hassan loyal to amir and regard him as his brother, and what moving me the most is that after the match hassan running the kite for amir and then he was stoping at the corner and facing the violent and he still said taht amir was his best friend and didn't hand in the kite.
But on the contrary, how did amir response hassan? He told lies to hassan just because he wants to be alone with his father, shouting at hassan when he was upset, and even saw hassan raping by other three children but give him a hand and at last run away. After that, he not noly mentaion about that and give no comfort to him, but also told lies to his father and hassan's father that he didn't know anything about what happened on that day.
So, we can see how brave and loyal hassan is and how cowardice and recreance amir is.