Gustavus was born in frontier Texas, September 4, 1857, in a small board house on a ranch, on Raney's Creek, Beat No. 3, near where the present site of Coryell County, now stands. He was the eldest son of Franklin Lafayette Miller (b. 1832, Millersburg, Tennessee; m. 18 Dec. 1856) and Emily (McGee) Miller (b. 11 May 1841, Jackson, GA), early pioneer settlers of that county. Interesting sketches of their experiences and accomplishments are given in Millers of Millersburg (1923) a family record published by Gustavus H. Miller in conjunction with J. Bailey Nicklin, Jr. He had two brothers, Felix Grundy Miller III (b. 17 Dec 1859; d. 18 Oct 1863) who died age three, and Franklin Lubbock Miller I (b. 21 Jan 1861), who later became one half of the Miller Brothers. He and his brother Frank were toddlers when their father died in army (CSA) camp in Galveston, Texas, 18 October 1862. Yellow Fever took Franklin Lafayette Miller, he never faced combat. In his book The Millers of Millersburg he Miller reminisced: "It is interesting to follow the illusive tracery in memory across that hazy span of life between the ages of four and seven. My father and Grandmother McGee died when I was about four years of age. I only remember to have seen my father going to the barn or attending to the stock--a colt or calf was prominent in my affection at that age. I only remember to have seen my grandmother when cooking. She must have encouraged me, her second grandson, in loving her, by giving me such dainties as she could prepare from meager after-servings. My grandmother's death lost her children a boundless love. My memory of these two ancestors is no doubt due to an inherited love of saddle and bridle, and a more primitive instinct to look for something to eat. I do not remember having seen my father about the house, or any game he may have played with us." His mother remarried, 20 March 1865, to James Franklin Mayfield (b. 20 Dec. 1846). The orphan brothers were raised in the crowded house of their maternal grandfather (James Lowery McGee b. 29 Dec. 1816, Jackson Co., GA d. 10 Jul. 1895, TX), along with the two groups of children sired by that worthy, and his surviving wife. Between the large number of mouths to feed, and depressed conditions following the Confederate loss of the Civil War, conditions for all the inhabitants of the McGee household were grim.