Graham O'Brien is a fictional character from the popular British television series Doctor Who. He first appears in the 12th series of the show, portrayed by actor Bradley Walsh. Graham is the step-grandfather of Ryan Sinclair, one of the Doctor's companions, and he often provides a sense of humor and wisdom during their adventures. In the series, Graham is characterized by his caring nature and protective instincts, especially towards Ryan and their friend Yasmin Khan. He brings a relatable perspective to the group, often reflecting on life experiences and the importance of family while traveling through time and space with the Thirteenth Doctor.