"Everyone" has to go back to the island. But they make no mention of Ji-Yeon (Sun and Jin's daughter) having to go back.

Is this because she was born off the island? [But she was concieved on the island, which would kind of seem to make her part of the island.]

Or is it a matter of producing the show? [Having the baby "with the grandmother in Seoul", is a convenient way not to need a baby during production of the show (the producers learned a lesson with the Aarron character).]

So, does Ji-Yeon have to go back to the island?

I know, We still dont know if Ji Yeon, Aaron or even Walt have to go back. I do hope they confirm this in the next episodes.

I agree with the idea that she was concieved on the Island, so that makes her part of the Island, unlike Aaron who was only born there.

But yeah theres a good way to get rid of her from the story, but that just would be cheap. If Jin's really alive, I see no reason than for Sun to bring her to see her father.

My theory is that neither Aaron nor Ji Yeon have to go back.

This is based on

the info from the Ajira Airways site for flight 316, which included 10 adults and 0 children.
I believe the ones who have to go back are Jack, Kate, Hurley, Sun, Sayid, Ben (but I don't know how, b/c he "can't" go back), John, Desmond, Walt (counts as an adult for airline pricing!), and Frank.

I know, We still dont know if Ji Yeon, Aaron or even Walt have to go back. I do hope they confirm this in the next episodes.

I agree with the idea that she was concieved on the Island, so that makes her part of the Island, unlike Aaron who was only born there.

But yeah theres a good way to get rid of her from the story, but that just would be cheap. If Jin's really alive, I see no reason than for Sun to bring her to see her father.

Hum, for some reason, I was assuming Aaron had to go back. Maybe I assumed that because Kate has him with her.

I've always assumed Walt does NOT have to go back. That (through Ben) the island "let them go" (Walt and Michael), but the O6 + 2 "escaped" unnaturally creating an imbalance.