John Weldon Koenig was born the son of the late John H. Koenig and Elva Oeding Koenig in O’Quinn, a community southwest of La Grange, Texas. After graduating from The University of Texas at Austin in 1958, he was commissioned as an officer in the United States Navy. During his naval career, he served on surface ships and nuclear submarines as well as naval staffs. He was in command of a nuclear submarine during the Cold War, and in 1984, was promoted to Rear Admiral. After serving his country for 31 years, Koenig retired from the Navy in 1989.

Since retiring from the Navy, Koenig has served as president of two companies. On January 1, 2000, he decided to devote more time to his family and to operate the K Bar K Ranch.

Koenig is the former chair of the Board of Directors for St. Marks Medical Center in La Grange as well as the Chairman Emeritus of the Board of Directors of the University of Texas Midshipmans Foundation. He also co-chaired the Fayette Library Museum and Archives Capital Campaign Committee. He is a member of the University of Texas Chancellors Council, The University of Texas NROTC Alumni Foundation, and the University of Texas Littlefield Society. He is also a Life Member of the Navy League, the American Legion, the Veterans of Foreign Wars, the University of Texas Ex-Students Association, and the Naval Order of the United States. He is also a member of the Longhorn Foundation and the La Grange Noon Lions Club. Koenig is a Son of the Republic of Texas. He and his late wife Nancy have three children and two grandchildren.  His children are Christopher, who is married to Cristina, Jennifer, and Andrew, who is married to Dawn. His grandchildren are Andrew Lee Koenig, Jr. and Kelsey Dawn Koenig.

Admiral Koenig was inducted into the College of Natural Sciences Hall of Honor in 2005. He is a member emeritus of the Board of the Battleship Texas Foundation and was selected as the 6th Distinguished Alumnus of the University of Texas NROTC program.