Who is Tariq in A Thousand Splendid Suns most similar to in The Kite Runner and The Thorn Birds?

I would argue that Tariq is most similar to Dane in The Thorn Birds and Hassan in The Kite Runner.
In A Thousand Splendid Suns, Tariq is the quintessential hero, courageous and always ready to defend those he loves. We get a glimpse of Tariq's fierce loyalty in Part Two, Chapter 18. When Khadim squirts urine all over Laila, Tariq confronts the bully. He takes off his prosthetic leg and beats Khadim with it while hopping on his one good leg. In Part Two, Chapter 25, Tariq fully demonstrates his capacity for loyalty when he pledges to return for Laila, even after she rejects his offer to marry.
There is no bitterness in Tariq because he understands Laila's reasons for rejecting him. He knows that Laila can't "wipe away the obligations of her life" any more than he can his. Tariq's ability to love, forgive, and trust exemplifies his moral stature.
Later, in Part Three, Chapter 44, we get further glimpses of Tariq's sterling nature. At the refugee camp in Nasir Bagh, Tariq's father dies, and his mother almost succumbs to pneumonia. Determined to save his mother from further suffering, Tariq does everything he can to secure employment. His main purpose is to earn enough so that he can move his mother into an apartment in Peshawar, preferably one that has "heating and clean water." However, no one will hire Tariq because of his crippled leg. In the end, Tariq takes on a dangerous job which lands him in prison.
Despite his difficult life, Tariq continues to stay positive. Even when he discovers that his Laila is a married woman, he betrays no ill-will towards the woman he loves. He understands why Laila married Rasheed, and his only regret is that he had to leave Laila behind years ago.
In The Thorn Birds, Dane is most similar to Tariq. Dane is an interesting character, actually. He is morally idealistic and fiercely committed to his Catholic faith. Like Tariq, he harbors deep convictions about life, truth, and religion. While Tariq is obviously Muslim and Dane is Catholic, both are similar in the sense that both are able to love unequivocally and without judgment. Both men are also willing to sacrifice their own comfort for others. In The Thorn Birds, Dane is also the perfect brother to Justine: he's supportive and loving. He loves his sister without reservation.
At the end of the novel, Dane dies of a heart attack after he valiantly saves two German women from drowning. Essentially, Dane made the ultimate sacrifice to his God. While Tariq doesn't die in A Thousand Splendid Suns, he and Dane share a compelling character trait: both are self-sacrificial in nature.
In The Kite Runner, Hassan comes closest to resembling Tariq. We are given glimpses of Hassan's self-sacrificing nature very early in the novel. Hassan serves Amir without reservation despite the latter's private contempt for him. Even after Amir betrays him by neglecting to come to his aid during his moment of greatest need, Hassan never displays any bitterness towards his friend. Like Tariq, Hassan is utterly incapable of holding grudges. In fact, Hassan suffers greatly after Assef rapes him, but he never reproaches Amir for his shameful betrayal. Later, Hassan takes the rap after Amir falsely accuses him of being a thief. Hassan sacrifices himself so that Amir can save his reputation before Baba.
Tariq, Dane, and Hassan exemplify all that is good and moral in the masculine soul; indeed, their collective humanity restores our faith in human nature.