Edward Mordrake was a 19th century English nobleman who had an extra face on the back of his head. According to the story, the extra face could neither eat nor speak, but it could laugh and cry.
Edward begged doctors to have his “devil twin” removed, because, supposedly, it whispered horrible things to him at night, but no doctor would attempt it. He committed suicide at the age of 23.
Also, Tom Waits‘ song “Poor Edward” is based on Mordrake.