Mark Twain’s only son who died in infancy was Langdon Clemens.
Langdon was the first child of Samuel Clemens, known as Mark Twain, and Olivia Langdon Clemens. He was born prematurely in November 1870 and remained weak and frequently ill during his short life. The family was living in Buffalo, New York, during part of this period.
Langdon died of diphtheria on June 2, 1872, at about 19 months old. His younger sister Olivia Susan, commonly called Susy, had been born only a little earlier that year. Twain and Olivia later had two more daughters, Clara and Jean, so Langdon remained their only male child.
The name can be confused with family names carried by Twain’s daughters: Olivia Langdon was his wife, and Clara Langdon was one of his daughters. Twain also reportedly blamed himself for Langdon’s death after a cold carriage ride, though that personal guilt was not a medical explanation for the child’s diphtheria.