What is the name of Sherlock Holmes' brother?

Sherlock Holmes’s brother is Mycroft Holmes. He is Sherlock’s older brother and appears in several stories by Arthur Conan Doyle, most notably “The Adventure of the Greek Interpreter” and “The Bruce-Partington Plans.”

Mycroft is presented as exceptionally intelligent, with powers of observation and deduction that Sherlock says may exceed his own. Unlike Sherlock, however, Mycroft dislikes physical investigation and “legwork.” He prefers to remain in London, where his broad knowledge and government connections allow him to solve problems from an armchair.

Mycroft is a founding member of the Diogenes Club, a famously quiet institution where members are expected not to speak to one another. He also works as a government official, and Sherlock suggests that Mycroft has access to important national information. His influence and intellect make him more than a simple supporting character.

Modern adaptations sometimes portray Mycroft as a secret-service figure, a rival or a comic foil, but the core details come from Doyle’s canon. Some later writers have proposed another brother named Sherrinford, but that character is non-canonical; Mycroft is the single standard answer to this question.