Answer by taking a quote from the following article:

Sherlock Holmes () is a fictional private detective created by British author Sir Arthur Conan Doyle. Referring to himself as a "consulting detective" in the stories, Holmes is known for his proficiency with observation, forensic science, and logical reasoning that borders on the fantastic, which he employs when investigating cases for a wide variety of clients, including Scotland Yard. First appearing in print in 1887 (in A Study in Scarlet), the character's popularity became widespread with the first series of short stories in The Strand Magazine, beginning with "A Scandal in Bohemia" in 1891; additional tales appeared from then until 1927, eventually totalling four novels and 56 short stories. All but one are set in the Victorian or Edwardian eras, between about 1880 and 1914.

Details about Sherlock Holmes's life, except for the adventures in the books, are scarce in Conan Doyle's original stories. Nevertheless, mentions of his early life and extended family paint a loose biographical picture of the detective. An estimate of Holmes's age in "His Last Bow" places his year of birth at 1854; the story, set in August 1914, describes him as sixty years of age. His parents are not mentioned in the stories, although Holmes mentions that his "ancestors" were "country squires". In "The Adventure of the Greek Interpreter", he claims that his grandmother was sister to the French artist Vernet, without further clarifying whether this was Claude Joseph, Carle, or Horace Vernet. Holmes's brother Mycroft, seven years his senior, is a government official who appears in "The Adventure of the Greek Interpreter", "The Final Problem", and "The Adventure of the Bruce-Partington Plans" and is mentioned in "The Adventure of the Empty House". Mycroft has a unique civil service position as a kind of human database for all aspects of government policy. He lacks Sherlock's interest in physical investigation, however, preferring to spend his time at the Diogenes Club. Holmes says that he first developed his methods of deduction as an undergraduate; his earliest cases, which he pursued as an amateur, came from fellow university students. A meeting with a classmate's father led him to adopt detection as a profession, and he spent six years after university as a consultant before financial difficulties led him to accept John H. Watson as a fellow lodger in 1881 (when the first published story, A Study in Scarlet, begins). The two take lodgings at 221B Baker Street, London, an apartment at the upper (north) end of the street, up seventeen steps.

Did he refer to his brother in his stories?
Mycroft has a unique civil service position as a kind of human database for all aspects of government policy.