Siger Holmes was the son of Brian Mycroft Holmes. He and his wife Violet Rutherford had at least eight children: Sherlock Holmes, Mycroft Holmes, Sigrina Holmes, Shirley Holmes, Sherrinford Holmes, Rutherford Holmes, Charlotte Holmes and Sigerson Holmes.
Siger Holmes was first named by William S. Baring-Gould in Sherlock Holmes of Baker Street. Baring-Gould's theories were incorporated by Philip José Farmer in Tarzan Alive.
Brad Mengel, in his article "Watching the Detectives, or The Sherlock Holmes Family Tree" (published in Myths for the Modern Age ed. Win Scott Eckert), identifies five other children of Siger and Violet: Shirley Holmes, Sherrinford Holmes, Rutherford Holmes, Charlotte Holmes, Sigerson Holmes, and Sigrina Holmes.
The Doctor Who novel All-Consuming Fire reveals that the Doctor had met Siger Holmes in India in 1843.