When Mildred G Trefethen was born on 9 May 1885, in Portsmouth, Rockingham, New Hampshire, United States, her father, Earnest Augustine Trefethen, was 20 and her mother, Nellie Elizabeth Mooney, was 19. She married John Brands Forbes on 1 January 1903, in Portsmouth, Rockingham, New Hampshire, United States. They were the parents of at least 2 daughters. She lived in Hartford, Hartford, Connecticut, United States in 1910 and Stratham, Rockingham, New Hampshire, United States for about 10 years. She died on 28 July 1958, in Exeter, Rockingham, New Hampshire, United States, at the age of 73.