My brother has recently tried to recover his account, unable to remember his details, he has the account name, cannot remember the email used for it. He has tried the recovery and added in as many details as he can, whats the likelihood of this working

Anyone but Njaguar, or maybe Kevin from staff will not be capable of doing anything but guessing
All you can do, is wait patiently for a response on the email
Pretty sure they wont discuss someone else' account with someone else but the owner