Just was thinking about this today, what do we actually know about Guybrush outside of the adventures we shared with him?
He’s just a random guy who showed up on melee island lookout point wanting to become a pirate.
What do we know, if anything, about his past?
Where is he from?
What age is he?
Who are/were his parents?
Is Lechuck actually his brother?
What was he doing before he came to melee island?
Why does he wanna be a pirate?
Most of your questions can’t be answered without knowing the story of the “real” third part. If we focus only on the first two games then some of your questions can be answered with the hints in the game(s):
Nothing much, actually.
America, near the Caribbean Sea (because I doubt that the parents would travel around the world at that time to visit a theme park). Maybe one can give a more detailed answer looking at the clothes of the parents.
A kid. In the games he is not quite yet an adult because there are jokes about his beard.
Here we have not enough information AFAIR. But you can see them at the end of MI2.
According to the second part: Yes.
If we consider his age: Nothing. He went to school and would like to be a pirate. 
Again, there aren’t enough information in the game, but: Who don’t wanna be a pirate (as a kid)? 
Maybe it’s the theme park from Pinocchio. 
Maybe the secret to monkey island is the answers to all these questions 
I read someone (with lowercase S) writing here about some early MI script where Guybrush talks about being English.
In fact I remember citing P.G.Wodehouse because Threepwood is a family in a series of novels of his.
Threewood…Thimbleweed…I´m thensing a thrend there…
Judging from the accent in the SE and Tales I would say american.
I would guess late teens early 20s
That bald guy and that old broad
Guybrush took the skull from his own parents and the Voodoo Doll worked. So obviously, yes!
Being an unconnected series of 0 and 1 until you booted up the programm.
To meet chicks. And it worked!
I question the explanatory power of that. 
The only thing we know for sure is that it’s LeChuck’s father. Guybrush could be a child from his mother’s first marriage. And let’s not summarily dismiss LeChuck’s claim that Guybrush is adopted. 
Well, in MI2 is pretty clear that he’s 19. So I’d say he’s 17/18 in MI1
Or just plain 9. Could it be… a reference to The Crying of Lot 49?! 
Oh yes, the wrong ID, of course! Yeah not sure how much time had passed between part 1 and 2.
Sure that comes always in handy when you need it.
I had a cousin who was not so bright that didn’t understand the joke there and insisted Guybrush is 21 in MI2.
What is the legal drinking age in italy?
If I’m not mistaken: to buy, 16 for beer and such, 18 for hard liquor.
To drink, I don’t think there’s an official minimum, unless it’s the same for buying. I mean, it’s not like in the USA where you risk a fine or jail time if you let your underage son take a sip of your beer.
By the way, it dawned on me quite “late” that he says 21 because it’s the American minimum age. But I just understood that he wanted to be declared older than he actually was, and he almost said his real age.
It turns out what I said is for Switzerland, not Italy. It seems that there isn’t an actual law in Italy, but usually they tend not to sell if you’re younger than 16.
Actually, people under 18 can’t buy take away alcohol. But if you are 16, you can buy alcohol that you must have on the spot.
This law came out in 2012 to comply with european rules.
it came out very late in comparison with US or other european country since alcohol addiction in Italy historically has been a minor problem, in comparison with these countries.
Recent statistics confirm this, and the total acohol cosumption is consistently decreasing in the last 10 years, but underline also that -especisally amongst youngsters- the use of wine is decreasing and the use of strong drinks is increasing.
Source (in italian, sorry): https://www.istat.it/it/files/2017/04/Consumo_alcol_in_Italia_2016.pdf?title=Consumo+di+alcol++-+12%2Fapr%2F2017+-+Testo+integrale+e+nota+metodologica.pdf
European rules? Unless the European rules say 16 is the EU minimum then it’d seem a bit odd that Austria, Belgium, Denmark and Germany have the normal 16 y/o drinking age.
The Netherlands upped it to 18 sometime recently and the results have been disastrous. Increased drinking and all that nonsense.
Why odd? I don’t know the european requirements, but every nation can make its own law according to it, so laws can differ from country to country.
As I mentioned, Italy has a 18 year limit for TAKING AWAY, but 16 limit for alcohol to be consumed on the spot. Here is the full list from which I took my data (sorry, I didn’t mention it earlier)
Odd because it’s the polite way of saying the statement doesn’t seem to make logical sense.
It’s 16 in many countries. The Netherlands as well as France changed it to 18 for stupid reasons wholly unrelated to the EU. Ergo, if Italy changed it to 18 that’s on Italy, not the EU.
Anyway, I looked it up and apparently the European Parliament did have a silly proposal like that, but it was rightfully struck down in 2005, 2007 and once again in 2015.