Sherlock Holmes and Mycroft Holmes are siblings, with Mycroft being Sherlock's older brother. Mycroft Holmes is a recurring character in the Sherlock Holmes stories written by Sir Arthur Conan Doyle. He first appears in "The Adventure of the Greek Interpreter," and later stories provide more insights into his character.
The dynamic between Sherlock and Mycroft adds depth to both characters and showcases their contrasting yet complementary qualities. Mycroft's character is intriguing because of his intelligence and influence in government, while Sherlock's adventurous spirit and keen sense of justice are highlighted in contrast. Overall, their relationship is one of mutual respect and camaraderie, and they share a strong familial bond as brothers.