If you watched Fantastic Beasts: The Crimes of Grindelwald, you would know how complicated things have gotten for the good guys as Grindelwald has won over not only Credence but Queenie (Tina’s sister) as well.
Grindelwald earned Credence’s favour by revealing him to be a Dumbledore, in fact, the long thought dead youngest brother of the Dumbledores. This, to avid Harry Potter fans, seems very out of nowhere because no one knew the Dumbledores of having another child but more so than that is the age difference between Credence/Aurelius and his “brothers”, but the fact remains that a phoenix did appear before him so he must be a Dumbledore.
There has been a new theory that Credence/Aurelius is the son of Ariana, Albus and Aberforth’s deceased younger sister. Now as far out as this may be it would explain Credence’s age.
So let me set the stage: Ariana is violated (raped) by the local muggle boys and her father murders a couple of them and goes to Azkaban. Aberforth and Albus are sent off to Hogwarts, unbeknownst to them that Ariana is pregnant, she gives birth and they send the baby away before the boys come back from school. Grindelwald arrives intrigued by the story finds one of the remaining muggle boys and forces him to reveal that it was indeed a rape, Grindelwald also hears rumors about a baby leaving the house of Dumbledore. Grindelwald cozies up to Albus they make their pact but now they are no longer friends and Grindelwald sets out to track the Dumbledore baby so that he can use him to defeat his old friend.
This would explain why Albus and Aberforth are currently unaware of him and also why they don’t bring him up in the future: too ghastly of a situation. This would also make Credence a Dumbledore.
We know Albus eventually gets the same phoenix Credence has, maybe he kept it as a reminder of his nephew and sister. It also seems like Credence’s story will probably have a tragic end but we don’t know for sure.