What are the essential events of Chapter 2 in The Kite Runner?

In Chapter 2, we get the back ground story on Amir and Hassan, who are children together. The boys play together, get into mischief together, and for the most past.... Hassan always takes the blame.

Hassan has a harelip, and he is teased bullied unmercifully by the other children. He is one year younger than Amir, whose mother died in childbirth. Hassan’s mother, however, ran away a week after his birth.