Hullen is the master of horse for House Stark. He has a son, Harwin.
Biography
A Game of Thrones
Hullen is present when the Stark boys find a deceased direwolf mother and laments that their presence does not bode well. Hullen goes south with Eddard Stark when he goes to King's Landing. Maester Luwin discusses with Robb Stark about appointing a replacement.
He is one of many Stark loyalists who is killed in King's Landing when Eddard Stark is arrested.