Jackie and Northwind Frost are the main antagonists of Ever After High special "Epic Winter".
Well the name meant to assure that Jackie and Northwind are the twin children of Jack Frost, they are both the servitors of the royal winter family, but Jackie and Northwind are tired to be on their service. And they go to Ever After High to take the breaking mirror glass powder, Jackie cursed both of Crystal parents to take over the kingdom with her brother, both of them tried to stop Crystal and her friends to get the seasons' roses to cured The Snow King and The Snow Queen, they seem to have succeeded at first, but Crystal and her friends finally defeated them, so, they are both punished to clean the snow in the street, much to Jackie deception to have failed to take over the kingdom.
They return in the webisode There's no business Like Snow Business as inventor of snowflakes, maybe again as punishment, Jackie said sarcastically "Its so enchatigly fun", when Northwind tried to tell that she didn't find it really fun she knock the snow bucket over his head to be sure he will contredict her. Even Maddie said if she was sarcastic, but they but convinced Maddie they loved it, and told her to give it a tried, but it was a big mistake.