Ralph Edwin Shannon was born in 1938 to Clyde and Elizabeth Lemiere Shannon, the eldest of four children. His parents were missionaries with the Unevangelized Tribes Mission, based at the rural station in Kajiji, Belgian Congo, near the Angolan border. The Shannons returned to the United States for their scheduled furlough in 1939. Unable to return to Africa due to World War II, Shannon's parents had an evangelistic ministry among French Catholics in Louisiana. It was during this time when Shannon was five or six that he was converted during a Bible club taught by his mother. With the conclusion of the war, the Shannons were able to return to Kajiji. Shannon lived on the station with his parents, and was educated through grade school by his mother, using the Calvert programmed learning course. Shannon returned to the United States, living in Monroe, Iowa, where he attended high school; his siblings were educated in a local boarding school which opened when Shannon was in high school. With the dissolution of the UTM in 1953, the Shannons returned to the United States. His parents then affiliated with the Mennonite Brethren, returning to Kajiji in 1955. Shannon entered Wheaton College in 1955 with a declared major of pre-med, intending to become a doctor. He graduated from Wheaton in 1959. He then went to Baylor University College of Medicine in Houston. Between his junior and senior years at Baylor, he was granted a fellowship to work as part of a study group on medical problems in developing areas of Latin America; his assignment was to Guatemala. While there, he met Ralph Winter, then a missionary in Guatemala. Shannon graduated from Baylor in 1963. While a student at Wheaton, Shannon had moved from his Baptist roots to Presbyterianism, and in 1964, Shannon was accepted for a three-year short term appointment (eventually four years) as a missionary doctor to Zaire by the Presbyterian US Board of World Missions. He was momentarily stationed at Lubondaie before he was transferred to Kinshasa for a government-required orientation. After completing the program, Shannon was returned to Lubondaie. He was then assigned to the medical station in Bibanga, where he developed his interest in ophthalmology. Shannon left the station three times during this term: first, for his wedding (See below); then for the birth of their first child, and lastly for an evacuation due to political turmoil.

Returning to the United States in 1968, Shannon began his study and residency in ophthalmology at the University of Pennsylvania in anticipation of establishing an eye treatment center in Zaire. He spent 1971 in Switzerland studying French, and returned to Kananga in 1972 to begin the eye program. The Shannons lived and worked in Kananga from that time, with furloughs in 1975-1976 (Decatur, Georgia), 1980-1981 (Decatur), 1985-86 (Wheaton, Illinois) and 1989-1990 (Wheaton, while Shannon studied at Wheaton College Graduate School in the Missions/Intercultural Studies program).

In 1966, Shannon married Elsbeth Johanna Scheidegger, a Swiss woman working as a secretary and administrative assistant to the Mennonite Central Committee in the Congo. The Shannons had four children: Cedric, Corrine, Scott and Stephanie.