Beaumont was born Charles Leroy Nutt in Chicago, the only child of Charles Hiram Nutt (an auditor of freight accounts for the Chicago & Alton Railroad) and Violet "Letty" (Phillips) Nutt, a homemaker who had been a scenarist at Essanay Studios. His father was 56 when Charles was born; Letty, his mother, was 22 years her husband's junior. Letty is known to have dressed young Charles in girls' clothes, and once threatened to kill his dog to punish him. These early experiences inspired the celebrated short story "Miss Gentilbelle", but according to Beaumont, "Football, baseball, and dimestore cookie thefts filled my early world".