Dumbledore ultimately overpowered Credence, but realised that he really was a Dumbledore - the son of Albus' brother Aberforth and thus Albus' nephew - after witnessing Credence's phoenix drop ashes on him.
Albus confirms to Creedence early on in the film that he is in fact a Dumbledore, quashing any rumor that Grindelwald had lied to the young boy in order to sway him to his movement. It is explained that Credence is the illegitimate son of Albus's younger brother, Aberforth (Richard Coyle).
Grindelwald knew Credence was Aurelius Dumbledore from the moment he realized Credence was an Obscurial (much like Ariana Dumbledore), and that he had survived the Obscurus for so long (which meant that he came from a very powerful wizard bloodline).
We learnt who Credence really is
At the end of the last film, Grindelwald told Credence he was really Aurelius Dumbledore – the previously unheard of sibling of Albus. However, that wasn't entirely true. While Credence is a Dumbledore, he isn't the brother of Albus, Aberforth and Ariana.
A child hidden from his father. A child who, like Ariana, could not control his magic. [narrator] But Aberforth, realizing that Credence is his son, used a magic two-way mirror to communicate with him, so that Aurelius might know his true family.
Credence Barebone Isn't Voldemort's Dad But He Could Be Snape's Grandfather.
It's left to Grindelwald to tell Credence his birth name: Aurelius Dumbledore. Thanks to Grindelwald's manipulation, Credence chooses to side with the dark wizard against his own family. He does, however, eventually reunite with his father, Aberforth Dumbledore.
Grindelwald later orders Credence to murder his uncle Albus Dumbledore in Berlin, claiming that the Dumbledores knowingly abandoned him. Credence stalks Dumbledore through the streets before confronting him, and the two duel.
It's thus unlikely Aberforth would open up about Credence without being prompted to. Since Harry doesn't know Aberforth had a son and Albus doesn't find it relevant for Harry in the context of the Second Wizarding War, it makes sense neither brother mentions Credence in the Harry Potter series.
More research proves that Alison was pregnant while filming, which could also explain things. Another fan noted, "Weight gain can truly change a person like night and day, even eyes and eyebrows can look vastly different!" Sadly, in April, Alison revealed that her pregnancy resulted in a miscarriage.
Kendra Dumbledore
Not only did her husband end up being incarcerated in Azkaban, but the whole family had to move from Mould-On-The-Wold, to Godric's Hollow to try and protect her youngest.
His mother is killed, and as a result Aberforth is unable to care for his son. Credence is taken to America and put up for adoption, a fact known to no one but Leta Lestrange (Zoe Kravitz).
Credence's costume and hair change are so similar to Severus Snape's that it foreshadows his path in Fantastic Beasts 3 — consequently ruining his ending. Grindelwald abused Credence's need for an identity, telling him whatever he wanted to hear to secure his loyalty in his war against Dumbledore.
He is the antihero with a tragic past and noble intentions - and Aberforth just confirmed it. Fantastic Beasts: The Secrets of Dumbledore confirmed that Credence Barebone/Aurelius Dumbledore (Ezra Miller) is the new Snape (Alan Rickman) through a very familiar line delivered by Aberforth Dumbledore (Richard Coyle).
Aurelius Dumbledore (born c. spring 1900), also known as Credence Barebone through adoption, was an English-born American half-blood wizard who lived during the 20th century. He was the son of Aberforth Dumbledore and an unnamed woman. One year after his birth, he unexpectedly was taken to America with his aunt.
In the sequel, she decides to join Gellert Grindelwald in his crusade on the promise that she can marry Jacob due to a law refusing to allow humans and witches to marry. However, Queenie turns to the side of good again and both she and Jacob marry each other in 1932.
No. Queenie is not Voldemort's mother. Voldemort's mother is Merope Gaunt, a British Pureblood witch who can trace her ancestry back to Slytherin and the Peverall brothers, specifically, the 2nd brother who had the Resurrection stone.
Another established rule that Fantastic Beasts 3 retcons is that the killing curse is supposed to be unblockable by any typical protective spell. At the end of Fantastic Beasts 3 though, Grindelwald attempts to use Avada Kedavra on Credence, but Albus and Aberforth Dumbledore successfully block it using golden magic.
There's been speculation he may have found her while in exile in Albania between 1981 and 1994, where he assumed a phantom-like form and possessed many animals (however, only snakes could bear him inhabiting their body). This could have something to do with his propensity to speak Parseltongue.
In the end, Credence/Aurelius returns to the light, taking sides with his family, rather than Grindelwald. The action has reverberating consequences, as Grindelwald tries to kill Credence, but Dumbledore protects him — breaking their blood pact.
I liked that they did not power up Credence to make this duel more epic but stayed true to Dumbledore defeating Credence with ease. This is where OotP failed. Dumbledore is the most powerful, or perhaps second most powerful, wizard of all time.
Nagini (d. 2 May 1998) was a Maledictus cursed to transform into a snake. Originating possibly in Indonesia, by 1927 she was a performer at the Circus Arcanus where she met Credence Barebone and had a romantic relationship with him.
Nonetheless, despite her initially benevolent nature, Nagini's blood curse eventually turned her into a snake permanently. Though it is unknown if she became evil as a result of that, or was turned evil as a result of Voldemort turning her into a Horcrux. As a snake, Nagini was completely loyal to Lord Voldemort.
Corvus loved this child, but felt that in order to protect him, he needed to send him away to America and give him up for adoption. We all know where that goes, and it leaves us with a tangle of questions. Chiefly, if Credence isn't actually Yusuf's half-brother as he thought, will he still feel compelled to kill him?
Service to Aurelius Dumbledore
In September 1927, Credence and Nagini met at the bird market in Paris, and stole some birdseed. Later that day in the afternoon, while on top of a derelict rooftop, Credence fed the birdseed to the phoenix chick.