In fanfiction, Harry Potter got to be raised by almost everyone so I am thinking why not to have Graves and Credence shot at it. I don't care if you fudge the timeline and have them live in the modern day or if they are old Graves and Credence.

Maybe one of them is related to him and Dumbledore has no choice but to send Harry to live with them.

Or the Dursleys go to America and since their babysitter bailed on them, they have to take Harry with them. Credence sees Vernon mistreating Harry, who reminds him so much of himself and his ma, he practically kidnaps him. And he asks Graves if they can keep the kid and Graves is like "Good Merlin, this is Harry Potter. I have my whole department looking for this kid!"