I don't get why so many people are sure about Guybrush's age in LeChuck's Revenge. All we have to go by is a dialogue option that says "Ninet... uhh, twenty-one." (or something like that) in response to the librarian asking about his age. How is this a guarantee that Guybrush is 19? Maybe he was just throwing that number out, but changed it to 21 to be able to get a drink at the bar.
Truth is, the first time I played the game I thought he was about to say ninety - because, if I recall correctly, he says "ninet..." and not "ninete..." - and since then I have dismissed the line as another silly joke. Maybe that doesn't make sense, but I was young, English isn't my first language, and I'm sometimes incredibly thick. My point is that it
could just be a joke, as could his guild membership card in Curse. Then again, all references to his age are probably jokes.
I always imagined him around 20 in Secret, quite a bit older in MI2 (22 or 23) and 25 in MI3. But those numbers are just how I originally perceived him, without Guruguru-lly over-analysing things.
Morgan is 22 or 23. That's what my gut tells me. I realise I'm not contributing much to the debate here, I'm just sharing my initial impressions. Sorry for the lack of substance.