By all indications, Dane O'Neill is most similar to Mariam in A Thousand Splendid Suns and Hassan in The Kite Runner.
While it's true Dane and Hassan are more sanguine in temperament and Mariam is more pessimistic in her approach to life, there is one commonality which links the three characters together: a selfless inclination to sacrifice personal comfort and safety for the benefit of others.
In The Thorn Birds, Dane is an easy-going and affectionate man. He has an open, welcoming nature that often endears himself to anyone he meets. As a child, his
habitual expression was a smiling one, his nature a curious combination of quietness and deep, sure happiness; he seemed to have grown into his identity and acquired his self-knowledge with none of the pain children usually experience, for he rarely made mistakes about people or things, and nothing ever exasperated or bewildered him.
As a grown man, Dane proves to be adept (even more than his mother, Meggie) in navigating a relationship with his difficult and often tempestuous sister, Justine.
Dane's optimism and habitual cheerfulness is the perfect temperament for a priest-in-training; his "natural tendency was to understand and forgive human failings in others, and be merciless upon them in himself." As a result of his moral stature and his warmth, Dane maintains an effortless connection with both his mother, Meggie, and his sister, Justine.
In the story, Dane dies while on vacation in Crete. After heroically saving two women from drowning, Dane has a heart attack that proves fatal. He dies as he exerts himself on behalf of the two women. He dies as he lived, sacrificially and selflessly.
In The Kite Runner, Hassan shares Dane's sanguine and forgiving nature. His loyalty to Amir is what compels him to sacrifice himself time and time again for his employer's son. When Assef threatens to appropriate Amir's kite, Hassan stands his ground. Despite Assef's cruel taunting about a Hazara's loyalty to a Pashtun, Hassan stands up for Amir and maintains he and Amir are friends. Hassan's courage is repaid by treachery on Amir's part and brutal violence on Assef's part. In the story, Amir remembers Hassan had the "look of the lamb" while Assef raped him. Essentially, Hassan sacrificed himself to save the kite he had retrieved for Amir.
Later, Amir, in a stunning act of betrayal, accuses Hassan of stealing his money and watch. Disregarding the pain inflicted on him, Hassan owns up to the theft, despite his innocence. The text tells us why:
This was Hassan's final sacrifice for me. If he'd said no, Baba would have believed him because we all knew Hassan never lied. And if Baba believed him, then I'd be the accused; I would have to explain and I would be revealed for what I really was. Baba would never, ever forgive me. And that led to another understanding: Hassan knew. He knew I'd seen everything in that alley, that I'd stood there and done nothing. He knew I had betrayed him and yet he was rescuing me once again, maybe for the last time.
Hassan's rape is a symbol of innocent sacrifice and the kind of sacrifice that is especially portrayed in Christianity, Judaism, and Islam.
In A Thousand Splendid Suns, Mariam gives her life in a sacrificial death in order to save Laila from sure execution. Despite her status as a harami (illegitimate child), rejected and reviled by the larger society, Mariam is an honorable and selfless woman. When Laila begs Mariam not to sacrifice herself, Mariam answers that she's lived life on her terms and she's proud to give herself one last time for those she loves.
"For me, it ends here. There's nothing more I want. Everything I'd ever wished for as a little girl you've already given me. You and your children have made me so very happy. It's all right, Laila jo. This is all right. Don't be sad."
She thought of her entry into this world, the harami child of a lowly villager, an unintended thing, a pitiable, regrettable accident. A weed. And yet she was leaving the world as a woman who had loved and been loved back. She was leaving it as a friend, a companion, a guardian. A mother. A person of consequence at last.
Hassan, Mariam, and Dane O'Neill lived for others. Their warmth, loyalty, compassion, and selflessness can be seen in the way they chose to decide their destinies in life.