Harry Sinclair was the older brother of Helen and George Sinclair.
His younger sister Helen found him difficult and patronising, leading their brother George to believe she did not like him, although that was not truly the case. After she left to travel with the Eighth Doctor, following the destruction of the National Museum's Red Lady collection in 1963, the two siblings never saw one another again. Sinclair had one son. By August 1998, Harry Sinclair had been dead for several years, having died of old age. (AUDIO: Absent Friends)