How do we know Amir and Soraya have a good relationship and strong kinship?
The protagonist and his wife in Khaled Hosseini's novel, The Kite Runner, Amir and Soraya each have secrets in their past of which they are ashamed. Soraya and her parents are afraid that her earlier affair and fling with drugs may have ended her chances for a proper Afghani marriage. Amir has several secrets--both concerning his friend/servant, Hassan--that torment him for many years. But Amir falls for Soraya at first glance, and her past does not bother him. Her attraction to him is sincere, and their love seems to grow as the years go by. Both of them deal patiently with their domineering parents, and Soraya shows great loyalty to her husband when he brings home his nephew, Sohrab, late in the story.
In the book "The Kite Runner" prior to their marriage Soraya shares her deepest secrets with Amir because she wants no lies between them. They are both two people who have carried worries from their past that have affected their outlook on life.
Amir marries Soraya and is very proud of her goodness. When his father becomes ill, she faithfully takes care of him until he dies. When Amir has to go to Afghanistan she supports his trip and does not hesitate to be a good wife. When Amir tells her about the child having to come home for them to raise she is again supportive.
Amir expresses often through the novel at how much he admires his wife.