Firstly, we need to understand where does your bro bought his monitor from. Usually those on display or have used before for event usually go at a cheaper price with lesser warranty.
Secondly, if acer provide 3yrs and your bro registered, acer MUST honor the warranty provided it's within that period. Else, email them.
Something here just doesn't add up, ur bro isn't telling u everything or u ain't telling us what u know.