Lord Walder Frey is patriarch to a brood of more than 100 descendants, a result of his many marriages. Ever resentful of his liege lord House Tully, he increased his family's stature by engaging one of his girls to Robb Stark in exchange for strategic access to a bridge under Frey control.
"Expect nothing of Walder Frey
and you will never be surprised." — Greatjon Umber