Standfast is a small castle, and is in fact more of a glorified towerhouse than anything. The Osgreys once had a glorious history as bannermen under House Gardener, and were named Marshals of the Northmarch for a thousand years. The only member of the house to appear was Ser Eustace Osgrey, who lived around 211.
Information about House Osgrey that reveals spoilers from the books.