Operation Rent-A-Brat

What if the Grimm Sisters' parents were kidnapped when Sabrina was only five or so, and Daphne was still a baby? What if the girls were separated and given to different, more permanent homes? What happens when William Charming wants to foster a kid to give him an edge in the upcoming election? He ends up with a child from the family he hates, of course! Too bad he doesn't know it.