See Grimm's Little Snow White, Translator's notes #2:
Some differences between the edition of 1812 and later versions:
Beginning with the edition of 1819, the Grimms add the statement that Snow-White's mother died during childbirth, and that her father remarried. In the first edition, presumably the version closest to its oral sources, Snow-White's jealous antagonist is her own mother, not a stepmother.
Are you fucking kidding me? It makes so much sense!
I wish I was a fairy tale historian or somethin'.