Dorothy Grace Bald Brandon Gilbert, daughter of Lillian Mallette Bald and Louis F. Bald, was born on October 4, 1901, in Jersey City, New Jersey. On November 10, 1908, Louis Bald died, leaving Lillian with three children, Ray, Dorothy, and Lewis. Four years after the death of her husband, Lillian met and married Ernest Brandon. Dorothy and her youngest brother were adopted by their stepfather and took his last name.
Dorothy Brandon graduated from Girls High School in Brooklyn, New York, in May 1918. In September of the same year, she entered nursing school at City Hospital of New York. There she met Dr. F.M. Gilbert, who was an intern at the hospital. The couple were married on November 17, 1920, and moved to her husband's hometown, Irving, Texas.