House Westerling of the Crag is an ancient westerlands house sworn to Casterly Rock, holding a ruined seat on a headland above the Sunset Sea. Their line is reckoned among the oldest in the west; they claim descent from the Age of Heroes, and the seashells on their sandy field recall the Westerling lords who kept their tower when the Iron Islands still raided freely along the western coast. Though never wealthy, they were counted proud, and in the age of the Dance of the Dragons the house reached its greatest height when Lady Johanna Westerling was given in marriage to Lord Jason Lannister of Casterly Rock. She proved the ablest ruler the Rock saw in that generation, holding the westerlands against Dalton Greyjoy's reaving after her husband fell at the Battle of the Red Fork, breaking the ironborn at Kayce with the remnant of the Lannister fleet, and governing as regent until her son Loreon came of age. An earlier daughter of the house was taken as one of the three Black Brides of Maegor I Targaryen, who wed her in the same torchlit ceremony as Queen Rhaena and Lady Elinor Costayne; she quickened by the king but died in a failed labour before the year was out.
At the opening of A Game of Thrones the house is held by Lord Gawen Westerling, whose seat at the Crag is half a ruin and whose coffers are lean. His wife Sybell is of House Spicer, whose people grew rich on the trade running between Lannisport and the Free Cities; the match was one of coin over name, and it sits uneasily on a house proud of its ancient descent. When Robb Stark stormed the Crag early in the War of the Five Kings, Gawen's eldest daughter Jeyne nursed him through an arrow wound and gave him comfort the night word came that his brothers were dead at Winterfell; Robb wed her at dawn to salve her honour, breaking his sworn oath to Lord Walder Frey of the Twins, and the consequences of that morning would seal the fate of his cause.