On this wiki (and implied in the TV series), whichever world a child is born in is the world that they're native to (e.g. Snow White was born in EF, so is native to EF). I believe that this description leves a couple of loopholes and continuity errors in the series. For example, Ashley and Sean's (Cinderella and Thomas') child Alexandra was born in Storybrooke, so according to the current beliefs, she is native to the Land Without Magic. In this case, in episode 3x11 "Going Home", when Regina reverses Pan's Curse and sends everyone back to EF (assumedly also those that aren't from EF e.g. Frankenstein/Dr. Whale) she states that because Henry was born in LWM, he wouldn;t come with them. In this case, those born on LWM, including Alexandra, would not be able to go back with them, and yet this loophole is left unexplained as Alexandra was seemingly brought back to EF, and taken back to Storybrooke in the Second Curse.
I believe that the answer to this issue is that is isn't the land in which the chils is born, but the land in which the child is concieved. This still keeps all characters native to the same land in which they are recorded as currently, but only changes Alexandra's native land from LWM to EF. This covers the loophole I uncovered. My explanation for why the characters said the land in which the characters is born in is simple, would you rather Regina say to Henry: "he will stay here because he was born here" or "he will stay here because he was conceived here"? It's easier and less awkward to say born than conceived.
Anyway, this is my theory and it fits in perfectly with the current storyline. Who agrees with me, or has suggestions of their own?