J.K. Rowling is not only famous for writing the Harry Potter series, but for everything that came after. The revelations about characters after the series was done, the added diversity after the fact, the yearly apologies for killing off characters. But none is so controversial as her revelation of Dumbledore's sexuality and his relationship with Grindelwald. Lost in all this though is what exists on the page. Dumbledore's quotes about Grindelwald in Harry Potter may not precisely confirm or deny what happened between them, but it does clarify their past.
All of these quotes are pulled from the final novel, Harry Potter and the Deathly Hallows. Though there are references to Grindelwald and Dumbledore throughout the series, beginning with that very first train ride to Hogwarts, Dumbledore does not directly address the subject until Chapter 35, "King's Cross Again." This scene, which takes place in a sort of limbo, sees Dumbledore confess to Harry all his faults, including how foolish he was in siding with Grindelwald as a teen.
However, because Dumbledore is talking to a teenager who is his student, and discussing it in a parental type way, he does not, ever, explicitly define the relationship. It's in the subtext, as they say. In the feeling, and the realization many times what we do for love can be terrible.
"I was gifted, I was brilliant. I wanted to escape. I wanted to shine. I wanted glory. Do not misunderstand me, I loved them. I loved my parents, I loved my brother and my sister, but I was selfish, Harry, more selfish than you, who are a remarkably selfless person, could possibly imagine."
"It was the thing, above all, that drew us together. Two clever, arrogant boys with a shared obsession."
"You cannot imagine how his ideas caught me, Harry, inflamed me. Muggles forced into subservience. We wizards triumphant. Grindelwald and I, the glorious young leaders of the revolution."
"Did I know, in my heart of hearts, what Gellert Grindelwald was? I think I did, but I closed my eyes. If the plans we were making came to fruition, all my dreams would come true."
"Invincible masters of death, Grindelwald and Dumbledore! Two months of insanity, of cruel dreams, and neglect of the only two members of my family left to me."
"I knew that we were evenly matched, perhaps that I was a shade more skilful. It was the truth I feared... I dreaded beyond all things the knowledge that it had been I who brought about her death, not merely through my arrogance and stupidity, but that I actually struck the blow that snuffed out her life. I think he knew it, I think he knew what frightened me. I delayed meeting him until, finally, it would have been too shameful to resist any longer. People were dying and he seemed unstoppable, and I had to do what I could."
"They say he showed remorse in later years, alone in his cell at Nurmengard. I hope that it is true. I would like to think he did feel the horror and shame of what he had done. Perhaps that lie to Voldemort was his attempt to make amends, to prevent Voldemort from taking the Hallow."
