Conversation so far:
Who were Sherlock Holmes' parents?
Sherlock Holmes' parents are not mentioned in the stories, although Holmes mentions that his ancestors were country squires
Did Sherlock Holmes have any siblings?
Sherlock Holme's brother Mycroft, seven years his senior, is a government official.
Did Sherlock Holmes only have the one brother?
Sherlock Holmes family consists of his one brother Mycroft

Question: Did he refer to his brother in his stories?
Self-contained rewrite: Did Sherlock Holmes refer to Mycroft in his stories?