Board Thread:Spoilers!/@comment-2153169-20140908192157/@comment-5925413-20140913200728

It's been revealed during the Frozen special that Elsa was born on the 21st December, for the winter solstice, and there originally was a scene (even a song if I remember correctly) where Elsa met her baby sister, born the 21st June, for the summer solstice. You can hardly be that precise if you're not a "biological" parent ;) (or a writer, which is basically the same thing)