Harry Potter: What Happened to Ariana Dumbledore?

Albus Dumbledore was undoubtedly one of the greatest wizards who ever lived in the world of Harry Potter. Throughout the series, he remained a mysterious figure, and many details about his life remained unknown until his death. One of these, to the surprise of many, was the fact that he had a sister, Ariana Dumbledore. Her existence was first revealed in The Deathly Hallows in Dumbledore’s obituary, written by his longtime friend Elphias Doge. It is mentioned that she had died shortly after Albus had finished school, but not much else is said about her. It is later revealed that she had a tragic life and died way too young, but her existence remains surrounded by mystery. What exactly happened to her? And why was her existence kept hidden for so long?