AST = Account Security Team.
Generally they only deal with the account holder, but they may make an exception here due to the circumstances. As long as you know the Apple ID, they may still be able to aid in resetting the password due to validation. If there was a credit card on the account, that may be one peice of validation they can use, though they will ask others.
After all, you don't want Apple to rest people's passwords for just anyone. I would not be surprised if this takes more than one phone call.
Account Security Team (AST)
Check the AppleCare number for your country here:
Call them up, and let them know you would like to be transferred to the Account Security Team.
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