"Twilight?" Princess Celestia was calling her name loudly, naturally prompting the princess of friendship to come briskly into the throne room.
"What is your bidding?" Twilight inquired, bowing.
"You don't have to be so formal," Celestia laughed. "You're royalty now, too."
"I apologise." said Twilight. "It's something no amount of time can aid in one getting used to."
"Has Princess Cadance left the city yet?" asked Luna.
"Her train is leaving any minute, why?" responded Twilight.
"There's no time to explain! You must get her and bring her back here!"
"My sister and I have something very important to confess to you and your friends, Twilight." said Celestia.
"I'll do my best!" Twilight assured the pair, and scurried off just as rapidly as her entrance had been. Celestia turned back to Luna.
"You really think we're right to tell them?"
"If our instincts are correct..." said Luna, nervously. She sighed. "Then there's no two ways about it, I'm afraid."
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"As many of you may have already rightly assumed," said Celestia hesitantly. The listeners - The Mane Six and Princess Cadance - were just as anxious as her and Luna. It certainly sounded like whatever she was about to inform them was extremely shocking and vitally important.
"...Luna and myself are not the first ponies to raise the sun and the moon."
"WHAATTT?" This shrill shriek came from Pinkie Pie, of course.
"Haven't you ever wondered who did it before the pair were born, over a thousand years ago, sugar cube?" Applejack asked her.
"I never really thought about it," admitted Fluttershy.
"It's true," said Luna. "Before we were born, our mother raised the sun in the morning and our father the moon when night came."
"Whatever happened to them?" asked Rarity.
"We've never really talked about this to anypony before," Celestia said increasingly slowly. "But...because of their immense and rarely-matched power...allicorns have a maximum lifespan of one-thousand and fifty years."
"Well...I didn't expect them to be immortal or anything like that..." said Twilight. "It's just that..."
"That's not the shocking part," warned Luna immediately. "The Cutie Map summoned both you and all of your friends here to Canterlot, Twilight, because this particular friendship problem has a cause all of you need to possess the knowledge of...before it's too late." Twilight and Cadance could feel their heart rate beginning to get faster. They were both struggling to prevent their mouths from gaping wide open. Twilight's friends were no better.
"Now comes the big confession," said Celestia sternly. Twilight, being the easily-perturbed pony she is, was having a troublesome time not crying out at this point.
"We have a brother," finished Luna. "He became an allicorn, like us...and controlled the stars...and was good...but one day...err...let's track this from the beginning."
"From when we were tiny little fillies, no bigger than Flurry Heart," continued Celestia. "All three of us knew that when our parents grew old and passed, we would be taking over their duties as governors of the moon and sun."
"Who governed the stars at that point?" inquired Cadance.
"Nobody," said Luna. "Our parents gave our brother...his name is Stellas Spatium...they gave Spatium the power to do so. Remember, before this point nopony really understood the concept of astrology and space."
"Yeah, that explains it, I guess." said Rainbow Dash.
"Anyway," continued Luna. "Shortly after the three of us were made either prince or princess of our natural satellites, Spatium grew made with jealously."
"Why ever would he feel that way?!" asked Pinkie rather uproariously. "Governing the stars sounds like a STELLAR way to go into nobility...pun intended."
"That's just it," said Celestia. "Spatium longed for a means of helping out the ponies in Equestria itself. While aligning the stars was a necessary task at this point, he didn't seem to think so. He wanted to...be proactive I suppose. He thought aligning stars was helping nopony, when in reality he was indirectly helping everypony."
"It drove him mad!" said Luna bluntly. "Over a period of a year or so, he became increasingly isolated from both us and our parents."
"He became so filled with anger and hate," continued Celestia, anxiety now very prevalent in her vocals. "That one day he resigned from his position and ran away from our castle in the Everfree Forest."
"He wandered in that forest for days," said Luna. "Eventually stumbling upon..."
"It can't be!" interrupted Twilight suddenly.
"What do your instincts say?" asked Cadance.
"The Tree of Harmony?!?"
"Right first time!" blurted out Luna and her sister simultaneously.
"But...I thought the elements were originally contained in the Castle of the Two Sisters."
"No," confessed Luna. "That came afterwards. They were always contained in their natural Tree of Harmony until Spatium got involved with them.
"You mean..."
"Yes," said Celestia. "I remember like it was only yesterday. Returning to our castle, Spatium used the elements to wreck it and drive us both out severely wounded."
"I thought the castle was damaged as a result of your battle with Nightmare Moon," said Cadance, bewildered.
"We were just getting to my not-so-not-evil form," said Luna. "And Spatium's powers..." Celestia took a heavy sigh.
"Forget everything you think know. Luna and I been pretty untruthful during the time you've known us both to hide the existence of our brother. What we're going to tell you will contradict much of what you believe to be true at the moment."