Battle of the Bears

In a world not entirely like our own, the polar north has been sectioned off as a kingdom for sentient polar bears and creatures of the like who were done with being treated as lesser by humanity. Vicious fighters, the bears are preparing to invade the nearby man-made cities if they continue to threaten the safety of their land and cross the borders into the Cold Lands. The chieftain's son of one of these communities and his hybrid polar-grizzly brother are among these warriors, with a burning hatred towards bipedal creatures until they are tasked with the raising of an orphaned child. Could their acceptance of mankind stop a war, or only worsen it?