Amir is the protagonist and narrator of Khaled Hosseini's 2003 novel The Kite Runner. He's an intelligent man, who's capable of being selfless and compassionate. However, he's emotionally confused when it comes to the relationships he has with his father and his best friend, Hassan. Amir fails Hassan by refusing to help him when he's sexually assaulted due to the pettiness and jealousy he feels towards Hassan, especially when Amir's father insinuates that he likes Hassan as if he were his own son.
Amir redeems himself when he shows that he feels immense guilt and remorse for not being a good friend to Hassan. He goes back to Afghanistan and adopts Hassan's son, Sohrab (who is also Amir's nephew), after Hassan dies. Unfortunately, Amir never gets the chance to reconcile with Hassan.
In The Thorn Birds, Amir is most like Father Ralph de Bricassart, who also betrays the love and loyalty of a loved one. While Amir betrays his best friend's trust, Father Ralph de Bricassart betrays and abandons his lover, Meggie; he sleeps with her and uses her funds to further his career as a priest. His selfishness and ambition become evident the moment he chooses the church over Meggie's love. As a consequence of his actions, Father Ralph de Bricassart never gets to meet his son Dane, who admires him as a priest, without knowing that Ralph is his father. Like Amir, Father Ralph also feels guilt and regret for leaving Meggie behind and, in the end, he's the one who leads Dane's funeral.
The polar opposite of Amir in The Thorn Birds is Luke O'Neill. Luke and Amir may appear alike in the beginning, as they're both selfish. However, unlike Amir, Luke never redeems himself, as he never changes as a person. He's manipulative, unkind, and doesn't know how to appreciate love; he's greedy and power-hungry, which is why he convinces the wealthy Meggie to marry him. Even though he and Meggie have a child, he never acts like a good father or a good husband—unlike Amir, who dedicates his life to Sohrab.
In A Thousand Splendid Suns, Amir is most like Jalil. Jalil is a good father to his children, especially Mariam, however he's not as kind to his wife Nana, who he casts out of the house when she becomes pregnant with Mariam. When Mariam comes to live with him after her mother's death, Jalil's wives don't accept her and he doesn't do anything to help, which is why Mariam is married off to the abusive and mean Rasheed.
In the end, Jalil realizes his mistakes and tries to redeem himself by writing a letter to Mariam, in which he reveals his deepest emotions and signs it with "your undeserving father" and even leaves her an inheritance, despite not being the wealthy man he once was. Unfortunately, Mariam never sees the letter, as she courageously sacrifices herself to save Laila and her family and takes the punishment for the murder of Rasheed. She's taken into prison for committing a violent crime and stoned to death by the Taliban. Thus, Jalil never makes amends with Mariam, similar to how Amir never makes amends with Hassan.
The polar opposite of Amir in A Thousand Splendid Suns is Rasheed. Rasheed is a violent, conservative and aggressive man, who lost his first wife and son. He marries the young Mariam and kills her self-confidence. He abuses her, both physically and verbally, as he believes that women are beneath men and serve only one purpose—giving birth to children. Unlike Amir, who grows up from a selfish and petty boy into an understanding man and a loving father, Rasheed stays bitter and cruel to the day he dies. After attempting to choke Laila to death, Rasheed is killed by Mariam.