Sun wants to know why he's telling her this now. "Because you deserve to know the truth," says Dr. Kim, who might want to consider that Sun is married to this supposed nutjob that he's so worried about pissing off. Sun stands there a moment looking stunned, and absolutely stunning. Fertility complications really suit her.
Back on the island, Jin's stunned (and, to be fair, also stunning). He sits down, and asks why she didn't tell him. "How could I?" she says. With one of the at least two languages we know you speak fluently? But a more pressing issue for Jin is that if he can't, then how? Sun looks at him and swears that she has never been with another man. Given her disbelief when she discovered she was pregnant, I'll give her the benefit of the doubt. Throw in Locke walking around on previously useless legs, and I believe her. It'd be nice if we could get a miracle or two explained, though. Jin thinks hard about it for a moment before stroking her hair, then saying, "Then it's a miracle," and they hug. Over Sun's shoulder, Jin's beaming. Over Jin's shoulder, Sun goes through about seven different moods, including anxiety and happiness and possibly constipation, before settling on relief.
Jin and Sun are both working in the garden. If I were Sun, I think I'd be putting my feet up with a big glass of lemonade while I watched my husband fix the garden he wrecked. They're discussing baby names, and decide to use a character from Jin's father's name, and one from Sun's mother. But no characters from any name of someone else they've slept with, right? Jin wants to know if they can tell people. Yeah, this early? No problem, right? Not that it matters, since half the island already knows, she tells him. Jin seems a little disappointed. Then it clicks. "'Daddy-o,'" he says, and nods, smiling. Heh. And he tells her that Bernard knows too. "Are you ready for lunch? Shall we go back?" She cautiously says that she'd like to stay another 20 minutes or so, by herself. Jin looks surprised, and he struggles with it, and she offers up the manhood-salvaging "if that's all right with you." He looks around, and then nods. He looks a little hurt, but then hides it and says he'll see her back at the beach. He starts to go, and then she casually says, "I love you," which stops him in his tracks. She herself seems surprised to have said it, like she hasn't said it in a while, not even when they were having all the hot reunion sex. Jin squats down, and kisses her. In English, he say, "I love you." She smiles at him.