In 1899, Stuart's father and his business partner, Henry Parsons Crowell, used a proxy fight to gain control of the American Cereal Company from Ferdinand Schumacher.
His son, R. Douglas Stuart Jr., was the founder of the America First Committee, which opposed United States participation in World War II, in September 1940.
Stuart was also long-time president of the Chicago Council of the Boy Scouts of America.
Stuart presented his credentials to Vincent Massey, Governor General of Canada, on July 15, 1953.
In addition to his son, Stuart and his wife had three daughters, one, Anne, who would go on to marry Nebraska politician Clifton Batchelder.