He apparently denied the terrible extent of his brother's criminal activities, as in the introduction to "The Final Problem" John Watson mentions that he has only written the story to counter "the recent letters in which Colonel James Moriarty defends the memory of his brother."
Moriarty Siblings Confusion
The stories give contradictory indications about Moriarty's family. In his first appearance in "The Final Problem" (1893), Moriarty is referred to as "Professor Moriarty" — no forename is mentioned. Watson does, however, refer to the name of another family member when he writes of "the recent letters in which Colonel James Moriarty defends the memory of his brother". In "The Adventure of the Empty House" (1903), Holmes refers to Moriarty on one occasion as "Professor James Moriarty". This is the only time Moriarty is given a first name, and oddly, it is the same as that of his purported brother. In the 1914 novel The Valley of Fear (written after the preceding two stories, but set earlier), Holmes says of Professor Moriarty: "He is unmarried. His younger brother is a station master in the west of England." In Sherlock Holmes: A Drama in Four Acts, an 1899 stage play of which Doyle was a co-author, he is named Professor Robert Moriarty.
Vincent Starrett author of the Sherlockian study, The Private Life of Sherlock Holmes (book) (no relation to the film of the same title) wrote that it is possible that Moriarty had one brother (who is a colonel and station master) or two brothers (one a colonel and the other a station master), though Starrett considered two more likely, and suggested that all three brothers were named James. Leslie S. Klinger (who annotated The New Annotated Sherlock Holmes collection) writes that Ian McQueen, author of 1974's Sherlock Holmes Detected: The Problems of the Long Stories proposed that Moriarty does not actually have any brothers, though Klinger himself suggests that Professor Moriarty has an older brother named Colonel James Moriarty in addition to an unnamed younger brother, and adds that Sherlockian analyst, collector and humorist John Bennett Shaw theorised that all three brothers were named James.
The premise that Professor James Moriarty has two brothers also named James has been used in adaptations and pastiches outside of Doyle's stories, such as the radio series Imagination Theatre's The Further Adventures of Sherlock Holmes (not to be confused with BBC4's radio series of the same title), and the manga and anime series Moriarty the Patriot.
- In Sherlock, Eurus Holmes makes reference to a brother of Jim Moriarty and claims that he works as a station master, a clear nod to The Valley of Fear.
- In Moriarty the Patriot, the manga's author used the two brothers theory, naming all three James Moriartys as William James Moriarty (the professor), Albert James Moriarty (the colonel) and Louis James Moriarty (the younger brother).
- Both Colonel James Moriarty (colonel) and James Moriarty (station master) appeared as antagonists in episodes of Imagination Theatre's The Further Adventures of Sherlock Holmes with Mr. Moriarty appearing in two stories trying to get revenge on Sherlock Holmes.