Robb stark, king in the north, with his loyal banner men behind, came to the twins and had to strike a deal with The freys to cross, he had to take an older Frey for a squire, foster two wards, when Arya came back she’d be wed to a Frey, and then walker Frey said that Robb would need to marry one of his grandchildren

“I’m sorry lord Frey but I’m already married” the young wolf said sternly and pridefully