Board Thread:Spoilers!/@comment-6175354-20150909224725/@comment-4427410-20150912175150

''  Snow and David seem to have a magical child and a non-magical child in the same union. ''

Emma's magic was the result of the curse that Rumplestiltskin had altered. He used Snow and David's DNA to alter the first curse and ensure that their unborn child would be the one to break it. Emma's magic was the unexpected result of what Rumplestiltskin had done.