Ah, for some reason I'd come away with the impression that he was younger, perhaps in his late 20's or early 30's. My bad.
No problem. I'd thought Lieutenant Commander, being equivalent to what I'm more familiar with, the Army/Air Force Lieutenant Colonel rank, was not necessarily a young person's rank unless there were a) battlefield promotions or b) significant peacetime below-the-zone promotions going on.
At risk of sounding stupid, was it merely his rank that suggested that, or was it something else I said? I'd be curious to know in case there's something in need of revision.