I think that the characters have been stuck in storybrooke not aging doing about the same thing from day to day, year to year, not exactly the same thing but sort of the mundane existence of life. Henry being in town has effect it because things happened like Snow gave Henry the book.
And i really think that the answer to why don’t they realize that they aren’t aging is simple they just don’t notice, the curse causes them to not notice. Henry noticed, but no one else does.
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