William Kennedy Smith is the second of four children of Stephen Edward Smith and Jean Kennedy Smith. His mother is a daughter of Joseph P. Kennedy, Sr. and Rose Fitzgerald Kennedy. He is the nephew of President John F. Kennedy, Senator Robert F. Kennedy, and Senator Ted Kennedy. He is the natural brother of Stephen Edward Smith, Jr. and the brother of adopted sisters Kym and Amanda.
Smith attended boarding school at Salisbury School in Salisbury, Connecticut . He received his undergraduate degree from Duke University (1983); completed premedical postbaccalaureate studies at Bryn Mawr College (1987); and attained his Medical Degree from Georgetown University School of Medicine (1991). He carried out his internship in internal medicine at the University of New Mexico Hospital in Albuquerque, New Mexico;
conducted his residency in physical medicine and rehabilitation at the Rehabilitation Institute of Chicago & Northwestern University, Chicago Illinois; and performed his fellowship in amputee care at the VA Lakeside, Northwestern University, Chicago, Illinois.
Currently, William Kennedy Smith is a board certified physiatrist and a trained prosthetist who has focused his research and practice on prosthetics and the care of amputees.