9. Dumbledore Has A Secret Brother - Fantastic Beasts - The Crimes Of Grindelwald
In the Fantastic Beasts series, the wicked sorcerer, Gellert Grindelwald, intends to use a dark energy called the Obscurus to slay Albus Dumbledore, believing he threatens his plan for world domination. When he learns a young magician called Credence Barebone has an Obscurus tethered to his being, Grindelwald manipulates him to join his cause.
Although little is known about Credence at first, we learn about his heritage in Fantastic Beasts: The Crimes of Grindelwald. In the conclusion, the titular villain reveals Credence is actually Aurelius - Dumbledore's long-lost brother.
Because the Harry Potter novels only refer to Dumbeldore having one brother called Aberforth, everyone was unprepared for this bombshell. Even though Potterheads expected this prequel series to have a few revelations about iconic characters, nobody saw this coming.
So, what does this mean? Is Aurelius going to turn against his own flesh-and-blood? Does Dumbledore know his brother exists? Is Grindelwald lying? Even though these questions should be answered in the aptly named Secrets of Dumbledore, it's safe to assume the follow-up will unveil even more epiphanies that will change the Wizarding World forever.