Unfortunately, you asked more than one question, so I had to edit it down to one.
One of the primary characters in The Kite Runner by Khaled Hosseini is Hassan; he is the son of Ali and Sanaubar, though we learn something different about that later (I do not want to give anything away if you do not already know). Hassan is a happy baby from the moment he is born, but his mother disdains him because he was born with a cleft lip. SHe runs away within a week of giving birth.
Ali is the servant to Baba, so he and Hassan live in a comparative shack on the back of the estate. Hassan, like his parents, is born a Hazara and has the distinctive Mongoloid features of that ethnicity.
Hassan has an intuitive sense of things; this ability makes him a thoughtful friend and an expert kite runner. These skills make him a valuable friend to Amir, but they also ensure that others will take advantage of Hassan.
Hassan loves the people in his life very much, and he loves Baba's son Amir too much for his own good. He is devoted to the slightly older boy, and Amir takes advantage of it. Hassan consistently tells Amir, “For you, a thousand times over,” and he means it. Hassan does not dissemble (lie), and he assumes everyone is like him.
And that's the thing about people who mean everything they say. They think everyone else does too.
Hassan sacrifices himself for Amir, and Amir lets him do it--more than once. Hassan is sent away from Baba's house for something he did not do, and Hassan establishes a new, quiet life in a small village. Later, after Baba and Amir are forced to leave Afghanistan, Hassan comes back to the city to help a family friend take care of Baba and Amir's house.
While he is there, his mother comes to see him, and he graciously meets and forgives her, another example of his selflessness with those he loves, even after they abused him. This selfless move back to the city, however, gets both him and his wife killed.
What makes Hassan such a good-hearted and loyal person are the same things which cause him much pain. Despite the pain and betrayals, he remains loyal and loving.