Col. Hemphill married his wife the late Elizabeth Anne ("Betty") Roach Hemphill in1942, while an aviation cadet at Mitchell Field in Stamford, Texas. He earned his wings and was subsequently commissioned an officer in the US Army Air Corps. He saw World War II combat service in the Pacific with the decorated 507th Fighter Group, flying his beloved P-47 fighter aircraft (nicknamed "The Flying Erector Set" because it was constructed from damaged aircraft parts). At the end of the war Col. Hemphill elected to remain in what became the US Air Force, serving for over 26 years as a pilot, judge advocate, operations planner, and diplomat. He held the designation of senior command pilot and flew a wide range of aircraft including the P-47, P-51, B-25, B-29, T-33, and C-47. Col. Hemphill had tours of duty in Palestine with the UN under the leadership of Dr. Ralph Bunche during the formation of the State of Israel; the Strategic Air Command (SAC) under the legendary General Curtis B. LeMay; the Fifth Air Force in Japan; the Office of the Air Force Chief of Staff in the Pentagon; and the US Army Command and General Staff College. Fluent in spoken Japanese, Col. Hemphill was proudest of his service as Air Attaché at the American Embassy in Tokyo, Japan from 1964 to 1967, serving under the leadership of US Ambassador Edwin O. Reischauer, the renowned Japanese historian. Upon completion of his Air Attaché assignment in Tokyo, Col. Hemphill received an award seldom given to foreigners, the Order of the Sacred Treasure, Third Degree, from the government of Japan in recognition of his distinguished service to both countries. He was also the recipient of the Air Medal with oak leaf cluster, the Distinguished Unit Citation, and numerous other military decorations.

Col. Hemphill was an active member and leader of several church congregations, including the Old Presbyterian Meeting House (Alexandria, VA), Tokyo Union Church (Tokyo, Japan), and Christ Church Uniting Disciples and Presbyterians (Kailua, HI). He authored or co-authored two church histories: A Church For All Seasons, Tokyo Union Church 1872-1972 (1972) and The Crossroads Witness (1988). Col. Hemphill was also a clever and gifted storyteller, and published a book of humorous children's stories entitled Harrison the Bunny and the Black Mysterious Gang (1992). He was also a prolific poet, and compiled a book of poetry entitled Hand Me Downs (1996).

Upon retirement from military service, Col. Hemphill lived in Hawaii for 20 years, serving as a legislative staff member in the Hawaii State Legislature. He subsequently moved to Olympia, WA, where he also lived for 20 years, writing poetry, gardening, listening to his beloved big band jazz, and raising a series of irrepressible beagles. Col. Hemphill moved to Paradise Valley Estates in Fairfield, CA, in 2007, where he continued to live independently. He was predeceased by his wife, Elizabeth ("Betty") Hemphill and his daughter Virginia Anne ("Gia") Adams of Alexandria, VA. He is survived by his sons, Robert F. Hemphill, Jr. of Potomac, MD and David F. Hemphill of Kensington, CA; his sister, Janet Lydia Jenkins of Lincoln, NE; and his dear friend Mary Jane Van Buren of Salt Lake City, Utah. In addition, Col. Hemphill is survived by four granddaughters (Megan and Claire Adams of Alexandria, VA; Lydia Hemphill of Oakland, CA; and Elizabeth ("Bizzy") Hemphill of Chicago, IL) and five great grandchildren (Aidan and Ainsley Simmons of Alexandria, VA; and Leo, Gus, and Daphne Confalone of Washington, DC).