Activation lock help

We have my grandson our old Ipad and his aunt set it up for him and she has no idea what email she used because she doesn't remember. It's been a while since this Ipad has been in use. We have try different accounts trying to see who his Ipad was linked to but are having no luck. My daughter no longer has the her old cell phone or number and neither do I. Do we don't nowhat to do. It's asking for the apple is and password sndno one remembers. Corey my grandson is 6 years old do one of id set it up, but we are having no luck in figuring it out.