Disambiguation: Uncle Marvel / Mentor
First published in: 1943
Uncle Dudley first appeared in Wow Comics (Fawcett, 1940 series) #18 (October 1943). He first appeared in a DC Comic in Shazam! (DC, 1973 series) #1 (February 1973). He has a niece named Mary Dudley, which means Dudley is his last name. He was finally given a full name, Dudley H. Dudley, in the 1990s.
Link: https://en.wikipedia.org/wiki/Uncle_Marvel