On my last FR flight, I saw the F/O doing the walk-around as I was walking up the front stairs to board the aircraft. I was seriously asking myself whether his parents had dropped him off at the airport! He didn't look old enough to have a full driving licence let alone a frozen ATPL. So it's interesting to read here that at least one FR captain thinks the same.
Guy Gibson was a Wing Commander at the age of 23. At the age of 25 he lead the dam buster raids. I don't think anyone said he was too young.
From an old Captain who enjoys flying with the youngsters even if I know nothing about Call of Duty Black Ops, house, garage, shed or even patio music.