During my long and intimate acquaintance with Mr. Sherlock Holmes I had never heard him refer to his relations, and hardly ever to his own early life. This reticence upon his part had increased the somewhat inhuman effect which he produced upon me, until sometimes I found myself regarding him as an isolated phenomenon, a brain without a heart, as deficient in human sympathy as he was pre-eminent in intelligence. His aversion to women, and his disinclination to form new friendships were both typical of his unemotional character, but not more so than his complete suppression of every reference to his own people. I had come to believe that he was an orphan with no relatives living, but one day, to my very great surprise, he began to talk to me about his brother.

It was after tea on a summer evening, and the conversation, which had roamed in a desultory, spasmodic fashion from golf clubs to the causes of the change in the obliquity of the ecliptic, came round at last to the question of atavism and hereditary aptitudes. The point under discussion was how far any singular gift in an individual was due to his ancestry, and how far to his own early training.

‘In your own case,’ said I, ‘from all that you have told me, it seems obvious that your faculty of observation and your peculiar facility for deduction are due to your own systematic training.’

‘To some extent,’ he answered, thoughtfully. ‘My ancestors were country squires, who appear to have led much the same life as is natural to their class. But, none the less, my turn that way is in my veins, and may have come with my grandmother, who was the sister of Vernet, the French artist. Art in the blood is liable to take the strangest forms.’

‘But how do you know that it is hereditary?’

‘Because my brother Mycroft possesses it in a larger degree than I do.’

This was news to me, indeed. If there were another man with such singular powers in England, how was it that neither police nor public had heard of him? I put the question, with a hint that it was my companion's modesty which made him acknowledge his brother as his superior. Holmes laughed at my suggestion.