See if they can recover the ID/password.
Apple ID - How to find your Apple An iCloud e-mail address is an Apple ID.
Apple ID - Find
Enter the Apple (iCloud) ID and click Forgot Password.
Apple ID - Manage
Apple ID – Forgot Password
If necessary, if they are the original owner, have them take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store.
Genius Bar Reservation US
or contact Apple ID Support. They will need to see the original purchase receipt/paperwork also.
Apple ID Support
Apple ID Support (2)
Apple Support by e-mail or chat
Apple Support using Twitter
Or fill out and submit this form.