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I wasn't able to find great cites for this, but many popular accounts credit Count of Tilly's dramatic loss to Gustav Adolph of Sweden at Battle of Breitenfeld to the fact that his second in command Graf Pappenheim leading the heavy Black Cuirassiers prematurely - and against orders - attacked Gustav's flank (being routed in the process), which in turn freed Gustav's cavalry to go after and capture Imperial artillery.
Tilly was born February 1559; and Pappenheim May 29, 1594, making them ~35 years apart (Making Tilly 72 in 1631, and Pappenheim 37).
Upvote:1
Fabius Maximus and Marcus Minutius come to mind, although their the age differential was most likely not more than 15 years.
For a reverse example, take Don Juan of Austria and Doria at the battle of Lepanto.