Former Illinois Sen. Adlai Stevenson III, a Democrat, has died at the age of 90, his family has confirmed. His son Adlai Stevenson IV said the Illinois Democrat had passed away at his North Side home in Chicago on Monday, and added that he had dementia. “He just faded away,” his son told the Chicago Sun Times. His wife of 67 years, Nancy, said the cause of death was Lewy body dementia. Stevenson is survived by Nancy and their two sons, Adlai IV and Warwick; two brothers, John and Borden; and nine grandchildren. Stevenson III seemed almost destined for a great political career, and was the great grandson of former Vice President, Adlai Stevenson, while his father, Adlai Stevenson II, was a former Illinois governor and two-time presidential candidate. He graduated from Milton Academy, Harvard College and Harvard Law School and served with the Marine Corps in Korea and was discharged as a …