Khaled Hosseini's novel The Kite Runner is set in and around Afghanistan during the period between late 1970 and 2003, and deals with family tension in times of war.
The character of Rahim Khan is complex; he is a friend of Amir's family and his father's business partner. In Amir's youth, Rahim acted as mediator when he and his father argued, and encouraged Amir to pursue his love of writing. Later in his life, when he is old and dying, he asks Amir to find Sohrab, Amir's nephew by his half-brother Hassan; Amir was unaware of the relation. At the end of the book, Amir reads a letter Rahim left him:
"...your father was a man torn between two halves, Amir jan: you and Hassan. He loved you both, but he could not love Hassan the way he longed to, openly... sometimes, I think everything he did, feeding the poor on the streets, building the orphanage, giving money to friends in need, it was all his way of redeeming himself. And that, I believe, is what true redemption is, Amir jan, when guilt leads to good."
(Hosseini, The Kite Runner, Google Books)
Rahim Khan, although not related to Amir's family, feels a deep connection with them, as well as the shame of keeping Sohrab a secret. He cannot find and rescue the boy himself, but he decides that if he gives Amir the knowledge and motivation to perform the task, it is as if he himself is doing it; through Amir, his final act is one of redemption. Rahim's long-held guilt has led to good.