Part 1 of 3 in the "Feathers and Gunsmoke Trilogy". Manga based. The characters are copywrited by Yasuhiro Nightow. I'm merely telling you the story Vash and Knives told me... ^_^

He had believed he was human. There was no reason not to believe, but now he knew better. He wasn't human, he never had been. All those months living with a human mother, with human emotions, learning human things, and it had been all for nothing. Or had it? Was his destiny based on what he was or what he wanted to be?
Vash stared out into the stars in space. They were always the same small dots of light. There was nothing unusual about them, they were always burning, always bright, and they never believed themselves to be anything but. The stars lit the black cloak of space and only at their deaths did they change what they were. Why couldn't he have had that too? He could have lasted without this knowledge until his death... But he wasn't even given the choice! His eyes filled with tears as he floated through anti-gravity. The little droplets hung suspended as perfect orbs in the air around him. Why had Rem waited so long if she had wanted to tell him? He had never even had reason to believe he wasn't exactly like her.

It had all happened so quickly. Rem had woken him up as she normally did in the morning and Knives stood by her side. His twin brother was always awake the moment Rem was, eager to follow her around the ship as she did all the rounds and checks on the ship's computers. Knives had been by her side since he learned to walk seven months ago. Rem took every moment of Knives' attention and just like any mother, tried to teach him everything she could. He learned by doing, even if it took weeks, Knives had learned every inch of the computer systems upon the ship. Vash knew he could learn it as quickly, but had only a mild interest in it from time to time. Even when Rem taught their lessons, he would often find himself contemplating the hundreds of sleeping people within the hull of the ship.
Vash never begrudged Knives anything. Not even this morning as they followed Rem into the Geo Plant, or "Recreation Room" as Rem enjoyed calling it. They would lie under the trees and feel the grass through their fingers. And eventually Vash had fallen asleep as he was apt to do, listening to Knives and Rem talk about the ship's inhabitants and about their mission, the SEEDs they carried through space. And Vash was glad that he was one of those seeds too, looking to find a place to call home, to sink his roots in.
He was thinking about the life of a flower as he laid napping, enjoying the artificial sunlight and feeling the brightness through his eyelids, when the sunlight was abruptly cut off. Aqua eyes opened slowly to peer into Knives' aqua blue eyes.
"What are you thinking about, Vash?"
Vash smiled, "How much I love it here and how much I'll love it when we all find a home together with the other SEEDs."
"Other SEEDs?" Knives asked as he continued to look into his brother's eyes.
"Well, yeah, of course Knives, the other people... The sleepers..."
Knives' eyes twinkled, "But we aren't people," he said gently. "It's no secret."
Vash sat up and his eyebrows furrowed. "What do you mean, Knives?" He looked at his fingers and down to his toes, and even lifted his shirt to look at his bellybutton. "I'm human just like the others... Right Rem? What's Knives talking about?"
Rem looked up from a book and her eyes were vacant as they sometimes were. She had been listening to the entire conversation as she always did, afraid of something, but Vash was never sure what. When she didn't answer him, Vash got up and went to her. "But you are our mother..."
A smile crept along Rem's mouth as if he had said something embarrassing. A hollow chuckle came from her throat and carried only a short distance. "Adopted, but yes, your mother in a way..." She looked at Vash's pained expression and melted, her head slipped down back to the book she had been reading. "But you and Knives... Aren't exactly human. Knives has known for so long that I assumed you already knew. I didn't even think to explain." Her dark eyes lifted to look at Vash through strands of her long hair. "Come here for a moment, Vash." She stood and held her hand out for Vash to take.
He looked at the hand a moment, then to Knives who nodded with a smile. "Rem... Vash should meet our real mother."
"I know..." Rem agreed with a slow smile. "Come with me Vash, there is someone you should meet." With those words, he took her hand reluctantly and followed her out of the Rec room and down through the many corridors of the ship.