Only daughter of Lord Tytos Lannister and Jeyne Marbrand, born at Casterly Rock in 245 AC and betrothed at seven to Emmon Frey, second son of Walder of the Crossing, when Lord Walder traded on Tytos's hunger to be loved and won the match at a feast before half the westerlands. Her brother Tywin alone rose to speak against it, and though Lord Tytos went white as mare's milk the betrothal stood; she never forgave the Freys for the seating and never forgot that Tywin had stood for her, even after the boy he had been hardened into the lion he became. She bore Emmon four sons, Cleos, Lyonel, Tion, and Red Walder, and ruled her inept husband with a sharp tongue and a Lannister will, claiming all four were his and daring any man to ask otherwise. After Joanna Lannister died birthing Tyrion she took a mother's place at Casterly Rock for the twins and the dwarf, ever pinching Jaime's ear, and once told Tywin to his face that of his three children it was Tyrion who most resembled him, for which he would not speak to her for half a year.
After the Red Wedding her son Tion lay murdered by Rickard Karstark at Riverrun and her son Cleos lay dead on the road from Maidenpool, and the Iron Throne attainted Edmure Tully and granted Riverrun to Emmon and Genna, though the Blackfish still held the walls. When Jaime came up the Trident to settle the siege she claimed her stool at his war council with a look that dared any lord to gainsay her, mourned Tywin before she mourned her cousin's gilded hand, and told her nephew plain that of Tywin's children it was Tyrion who had inherited his cunning, not Jaime, and that this was what frightened her most now that her brother was dead. She counselled Edmure's death and feared the unborn Tully child, would sooner have had Darry than Riverrun for the extinction of its male line, and once Edmure yielded and the Blackfish slipped the noose she bid Emmon hold the castle or burn it, settling at last as Lady of Riverrun with two hundred men and a singer named Tom of Sevenstreams whose loyalties she did not know.