In The Kite Runner, Farzana is a minor character who appears only briefly. Her marriage to Hassan is not explored in any detail. From what the reader sees, however, it is a loving marriage between two good people, making the best of atrocious circumstances. In chapter 17, they are both murdered within moments of one another, dying under the same oppression which blighted their lives.
In The Thorn Birds, the most similar marriage to that of Farzana and Hassan is probably that of the kindly Luddie and Anne Mueller, who are also generous, sympathetic, and self-sacrificing, though their lives do not end in tragedy. The polar opposite of Hassan's marriage to Farzana is the abusive and loveless union, based on mutual dishonesty, between Luke and Meggie O'Neill.
In A Thousand Splendid Suns, the most obvious parallel is with Hakim and Fariba, who also die in the same tragedy and who are similarly affectionate spouses and doting parents. The polar opposite is Rasheed's marriage to Mariam, which is not only arranged but compelled, and in which Rasheed is an atrocious husband, and not much better as a father, at least to his daughter. The tragic death of both parties is, in this case, caused by internal weaknesses in the marriage, rather than by uncontrollable force from outside.