Guillermo Jones was 38 when he won the WBA belt at cruiser. Holyfield and Gassiev were 23 when they won their first cruiserweight titles I think so I'd guess that they're the youngest. Correction: Jones was 36. As was Virgil Hill so maybe they take the title of oldest men to win a cruiserweight title
Giacobbe Fragomeni was 40 when he lost his belt to Zsolt Ederi. He was probably the oldest with Holyfield being the youngest.
