Fantastic Beasts 2 Ending And Twist EXPLAINED
3. There's Probably A Second Twist Coming
Right now, there's no actual confirmation that what Grindelwald says to Credence is in fact the truth and if you look at the timeline issues that his existence causes, you might start to wonder whether this isn't all an elaborate ruse to weaponise Credence against Dumbledore. After all, we didn't see any confirmation from Albus that the story of his brother is even real and it wouldn't exactly be nice of him to wipe him out of memory.
Also, if he existed, why wasn't he dug up by Rita Skeeter when she got all of her information out of Bathilda Bagshot? If that famed historian knew the deep, dark secret of Ariana's death and Aberforth's fancy for goats, why the hell wouldn't she know about the existence of a third son? This makes no sense even, unless you just assume that Bathilda decided to lose interest in the Dumbledores as soon as the far more interesting dynamic appeared between Grindelwald and Albus during the wizarding war. Because, famously, historians hate interesting history.
So, let's assume that it doesn't make sense because it's not true. There's more evidence to suggest that it's impossible.
For Aurelius to be a Dumbledore, he'd have to be the offspring of either Percival or Kendra. Percival died in Azkaban in sometime later than 1890 (possibly up to 1900), Kendra died in 1899, right now Credence's birthdate is established on the Harry Potter wikias as 1901 (and the Fantasic Beasts 2 script states that the ship he's on sailed in 1901), so he can't have been Kendra's.
The only logical assumption is that he was born to Percival and another woman in Azkaban, because the prison's rules on prisoners boinking were lax enough to allow it. But even then, Ezra Miller stated that Credence was 18 years old in Fantastic Beasts and thus had to have been born in 1908 or 1909. For him to have been born in 1901 or before to fit the Dumbledores being alive, he would have to have been 27 or older during Fantastic Beasts. And that's impossible since he's still living with his abusive adoptive mother in the first film and definitely is not a fully-grown adult.
So something is up here - either Grindelwald lied or the timeline is ruined OR Percival Dumbledore didn't die in Azkaban as suggested and he escaped and had a child later than we assume. The most fitting and elegant solution that doesn't mean all of this writing is broken is that Grindelwald has invented the Aurelius Dumbledore story.
Sadly, the problem with that is that a phoenix appears to Credence, basically confirming that he genuinely IS a Dumbledore, but that doesn't mean that there's not probably going to be a second major twist for this to even be possible. It's just what that twist is going to be that's confusing right now.