House Grayson is a possibly extinct vassal house from the North of Westeros, holding allegiance to House Stark of Winterfell. They are mentioned briefly in Game of Thrones: A Telltale Games Series, to which they are unique.
During a meeting of Ironrath's small council, Lord Rodrik Forrester may ask about the state of House Forrester's allies. Duncan Tuttle responds that House Grayson, along with Houses Elliver and Brownbarrow, were wiped out at the Red Wedding.
In the books
Unlike the Forresters and Whitehills, House Grayson seems to be purely an invention of Telltale, much like Houses Branfield and Glenmore. The same is true for their allies, Houses Elliver and Brownbarrow.
Houses from the North