House Cerwyn of Castle Cerwyn holds a modest keep half a day's ride south of Winterfell, set on the kingsroad to mark the last stop before the great castle. The Cerwyns have been the Starks' nearest neighbours longer than anyone alive can remember, and a Cerwyn lord can usually be at Winterfell within a morning if Winterfell calls.
Lord Medger Cerwyn is one of the first to answer when Robb Stark calls the banners, with three hundred men at his back and his son Cley, scarcely older than Robb himself, at his side.