Had the original request been authorised?
If not, and you'd want to know why it took them 3 months to come up with an answer.
The fact noone else is off is baffling as its not as if hes leaving them in the lurch, Id advise him to see the HR person or whoever it is and put his case forward.
If as you say none of his colleagues have a problem with him having those weeks, then get them to back up his case.
As advised above he needs to look at the companies holiday request/refusal etc statements