In the book "The Kite Runner" Amir and Hassan have grown up together. They have even nursed from the same mother. Everyday Amir climbs out of bed to get ready for school. Long before he goes to the table Hassan has been up helping set the table for Amir's breakfast. Hassan irons his clothing and serves him his food.
The two boy's play together and Amir reads to Hassan, but they have a line that separates them. Hassan is a Hazara child, which means that Amir identifies him as being beneath him. When Amir's other friends come over, he does not invite Hassan to play.
Although they are very close and have a lot of fun together, Amir is also jealous of Baba's affection towards Hassan. Amir identifies that Hassan is a servant not a brother or friend.