Ummm, the Marines don't have admirals, and you should make captain in the Marines pretty fast, since it's only O-3, as opposed to O-6 in the Navy. You sure he wasn't in the Navy?
When I think about it, I think he was an enlisted man in the Marines for Vietnam, then an officer in the Navy. He left the military service somewhere in the 80s.
This is a much older brother that I am not close to.
And note that Navy (or Coast Guard) Captain is understandability a much higher rank than in the other services, O-6, Colonel elsewhere, the last rank before flag AKA General or Admiral. I can see an unofficial requirement for reaching O-6 before 40 for then being in the running for flag rank.
