I don't think Jin is dead. He is probably still on the island. The fact that Sun called out for Jin when she was going in labor makes me think this. Yes it could have been b/c she was delusional and missed him. But couldn't it also be because he is still alive and she forgot that he is not with her. I had that feeling even before I saw the dates on the tombstone. Even the way her and Hurley interacted made me think that he isn't really dead, he just isn't rescued with them.

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Because all we really need to survive is one person who truly loves us. And you have her.