Harry's previously unknown younger stepbrother, Will Sullivan (also a medical doctor), appears in the second series of the "Sarah Jane Smith Adventures" (2005–2006) audio plays by Big Finish, voiced by Tom Chadbon. Harry is mentioned by both Will and Sarah Jane, but he is apparently on some secret assignment and neither has seen him for a long time. Will is eventually revealed to be a sleeper agent of a religious cult targeting Sarah Jane, and dies during the course of the series.