George Howard Brett was born in Cleveland, Ohio on 7 February 1886, the second of five children of William Howard Brett, a notable librarian, and his wife Alice née Allen. George's older brother Morgan graduated with the United States Military Academy at West Point class of 1906, and served for many years as an ordnance officer, retiring in 1932 as a colonel. The family was unable to secure a second West Point appointment, so George Brett graduated from the Virginia Military Institute in 1909 and was commissioned as a Second Lieutenant in the Philippine Scouts on 22 March 1910. While in the Philippines he transferred to the US Cavalry on 10 August 1911, joining the 2nd Cavalry.