Lord Walder Frey was patriarch to a brood of more than 100 descendants, a result of his many marriages. an attempt to increase his family's stature by engaging one of his girls to Robb Stark failed when Robb broke his promise. Unsatisfied with King Robb's attempts to make amends, Lord Walder wreaked his vengeance by massacring his Stark guests at the wedding of his daughter Roslin to Edmure Tully. Arya Stark, using skills learned from her time in Braavos, reminded walder Frey of his treachery and served him a pie made from his sons before killing him.
Black Walder Rivers
A bastard son of Walder Frey, Black Walder is so known because of his dark temper. He accompanied his brother Lothar to Riverrun where they met with Robb Stark to negotiate the marriage of Edmure Tully totheir sister Roslin. On the night of the wedding, Black Walder slit Catelyn Stark's throat. Arya Stark, using skills learned from her time in Braavos, killed him and served him in pie to his father, Walder Frey.
One of Walder Frey's many sons, Lothar accompanied his brother Black Walder to Riverrun where they met with Robb Stark to negociated the marriage of Edmure Tully to their sister Roslin. On the night of the wedding, Lothar stabbed Robb's pregnant wife Talisa inthe abdomen, thus initiating the massacre of the Red Wedding. Arya Stark, using skills learned from her time in Braavos, killed him and served him in pie to his father, Walder Frey
Roose Bolton's new bride, Walda was a granddaughter of Lord Walder Frey. Bolton specifically chose the heavy-set young woman because Lord Walder promised him a dowry equivalent to his wife's weight in silver. After walda gave birth to a son and put Ramsay's birthright ar risk, the bastard murdered the baby, his stepmother and father.