Fantastic beasts: the crime of Grindelwald ended with a rather big surprise in the last moments that are changing Harry Potter canon forever.
[[[[Followed by connectors]Throughout the film, the ornate Credence Barebone (Ezra Miller) searched for his true identity in Paris. Lovers and even some other characters have assumed that Lete Lestrange, a long-lost brother (Zoe Kravitz), was long lost. Except for the year, she actually replaced her distracted child with her younger brother with another, quenched child while on a sea trip, and her real brother was then tragically drowned when the ship sank during a storm (The crime of Grindelwald is not a film that is just shy about killing children). In the final moments of the film, Gellert Grindelwald (Johnny Depp) reveals the real name Credence is Aurelius Dumbledore and says that his "brother" (probably Albus) is trying to kill him. There are also phoenixs that previously remember us in the film, they always come to Dumbledore, which he needs (although it is not clear why now, when in such a great danger and drama, the magic creature came to Credence now).
According to the Harry Potter books, Albus has only one brother (Aberforth). He also had an upset sister (Ariana), who was apparently Obscurial (just like Credence). It was unluckily killed during a duel between Albus and Grindelwald, an incident Albus had difficulty assessing since then.
Dredstav, who is Dumbledore, helps explain his exceptional magical ability and personally connects him with the enemy Grindelwald, who is moving forward. Albus can potentially add another opportunity for salvation – he could not save Ariane, but maybe he could save Aurelius?
(Fun fact, possibly coincidence: The name Aurelius has a link to the first actor who played Dumbledore: Richard Harris also played a convicted Marcus Aurelius in Gladiator.)
That's what we know. What we do not know is pretty much everything else. Disclosure raises the tone of the questions and, according to the nominal value, does not seem reasonable. But let's take a closer look.
First, we assume that Grindelwald is telling the truth. I could lie, of course, but that's unlikely. Rowling's great disclosures at the end of her novels are usually true, because otherwise, what's the point? But it's also hard to imagine why the brother never mentioned one of the most famous magicians of all time (how could this be missed by Rita Skeeter?). The situation is not contrary to the controversial move of the second prequel, Star Trek: Discovery, and the decision to accept Spock's adopted sister.
According to The Rowling Library, they do not match the age. Father Albus, Percival, were sent to Azkaban prison and died there a year before Albus went to Hogwarts – so he was a future professor and director for about 10 years – and Credence and Albus are definitely more than 10 years apart. (But, Crimes of Grindelwald also shows the young Minervo McGonagall, who works in Hogwarts, although her character was apparently born a few years after the film).
It is also unclear whether Albus knows that his brother is a Credence. Someone would have assumed this, because Albus seems to know more about Credence than it says accent, and usually is the smartest character in the room. But if Grindelwald says it is true, and Albus knows it, it's hard to imagine that Dumbledore will defend the action plan Crimes which could lead to the death of his brother.
There are theories. Perhaps Ariana's Obscurus has Credence and this is Grindelwald's "brother", which refers to? Perhaps Credence is actually Arianin's secret son (but who is "brother"?). Would Albus's father dash Aurelius to Azkaban? (When sex with Dementors rotating around, it seems quite difficult to pull it.)
One thing is certain: Rowling would not have made this move without a clear explanation. If we want to know for certain, we will have to wait for the third film in the series, which is expected in 2020.