Joy Hill

Natural daughter of Ser Gerion Lannister, got upon a common woman named Briony and given the bastard name of the westerlands. Raised at Casterly Rock after her father sailed east in search of the lost Valyrian sword Brightroar and was never heard of again, she grew up among her trueborn cousins as the only child of the Rock, a sweet child by Ser Jaime's reckoning and a lonely one. Lord Tywin pledged her hand in the secret pact with Lord Walder Frey that bought the Red Wedding, promising her to a natural son of the Crossing once she came of age. After the siege of Riverrun Lady Sybell Spicer pressed Jaime for the bride from Casterly Rock that Tywin had promised her eldest, Ser Raynald Westerling, and Jaime understood his father had meant Joy, though Sybell balked when she learned the lord had offered her son a bastard.