George being gradually introduced to public duty at a young age did not start with Diana introducing William and Harry to public duty when they were George's age. The future Queen Mary was helping her mother, Mary Adelaide, with clothing drives at that age, and the late Queen Mother started helping her mother with various charities when she was even younger than George is now. The late Queen and her sister regularly accompanied their parents on Royal engagements, as did Charles and his siblings. Diana was just the latest one.