It's a rainy day in Equestria and Discord is visiting Celestia at the castle. They're walking down the dark hallway when he asks her to tell him the story of how they came to be friends and also to tell him about his family and how he became the last of his kind.
"Fine, I'll tell you, I was bound to have to tell you the truth eventually," sighs Celestia. They go into her private study and they sit down. There she tells him everything.
"When you were little," says Celestia as she pulls out a book on Draconequine history, "you were one of many. You had a mother, father, and sister who loved you. Everything was perfect. You weren't known as Discord yet either, that was a name ponies would give you later. Your family simply called you Dantusko, which translates into "keeper of chaos". Your sister was named Dialina, which translates into "beautiful gem or fair, precious stone". You were happy. Your kind were happy with not a care in the world. One day, though, that changed. The creature known to you simply as the dragon slayer, came through and killed your family right in front of you. Luna and I watched as it happened from behind a bush. My sister wanted to jump in and help you, but I forbid her. We watched as you ran off terrified into the woods not far from where we were hiding. Once the dragon slayer had gone, we left the bush and went and found you crying in the woods. We then took you home with us to the castle and introduced you to our mother and father, Queen Galaxia and King Orion. We then adopted you as our brother. The three of us grew up together. We were inseparable, especially you and Luna. You two would always play hide and seek while I was off studying as I was the eldest child. Once I got done with my studies for the day, then I'd join in on your fun. The three of us had the best of times. Even so, I knew it wouldn't last forever. I knew eventually you'd live up to your name and become the chaotic creature known to all as Discord."
"What was the dragon slayer's real name?" asks Discord.
"You may know him better as the magic stealing centaur Tirek," replies Celestia bowing her head, eyes closed.
"Tirek killed my family," says Discord, "he killed the rest of my kind."
"Yes," replies Celestia. "I'm sorry you had to find out this way."
The two then go and walk around Canterlot since the rain has finally stopped. As they walk, Celestia continues to tell Discord of his kind. "Your kind wasn't meant to be chaotic," sighs Celestia, "your kind was meant to be good and a neighbor to ponies and all the other creatures in Equestria. Your kind was meant to be kind hearted, generous, beloved by all. But the scars losing your parents and sister put on you was too much and it caused you to snap and become the chaotic creature you are today."
"I...I had no idea..." responds Discord.
"You wouldn't, since Luna and I have been trying to lie to you about your past since day one," replies Celestia, "and sometimes we feel like it's our fault that you're this way."
"But it's not," replies Discord.
"But it is," replies Celestia as she bows her head, "it's all our fault."
"Please, continue with the story," replies Discord. "I want to know more about my mother, my father, my sister..."
"Your mother and father were the king and queen of the Draconequine race. Their names were Galavere, which means "daughter of a noble birth", and Cordonious, which means "son of the cobra". They ruled the lands we called The Beyond until the day Tirek struck them down. Once your parents were out of the way, Tirek came after you and your sister. He killed your sister but spared you because he saw you as an asset and a potential ally someday. Once he killed your sister, he continued to take out the rest of your kind one by one. Ravendawn, the elder of your people, was the last to die, but he died with great honor."
"I remember Ravendawn, he was like a brother to me," replies Discord as he hangs his head and lets a tear fall from his face.
"I thought you might," replies Celestia. "He was a great and fair creature. The perfect example of your kind and what they were supposed to represent."
The two then go out onto the balcony and Celestia lets Discord soak in all the new information. Once he has, he begins to cry and she comforts him as best she can. She looks into the sky in the distance as a rainbow forms overhead. It's the start of a new day, a new chapter, but deep down inside, she knows for Discord, things are beginning to change and become more clear than ever before.