Ok, I swore I'd never write a fan-fic about Harry Potters secret sister, but just give it a chance, I implore you. Please tell me what you think, I'd appreciate it. I have posted this already to Wattpad, but have decided to post it here as it reaches a broader audience.

This is not a happy story. It does not have a fairytale ending. This is the story of love, hate, anguish, bravery, fear and above all else, a story of sacrifice. This is the story of how Severus Snape tore history in two unwittingly. This is the tale of Felicity Evans, Harry Potter's younger sister. A sister that was never supposed to be.

Lily Evans never gave up on her best friend. She would always send him owls, even though he would never reply. She often wondered if her ever received them. Many times she begged James to forgive Severus, because she had forgiven him and felt that her husband should, too. When they had their first son, Harry, she was ecstatic, she wanted to tell everyone she knew that was important to her. She sent an owl to Severus, too, worried about his reaction, but there was none. Several months later she got some amazing news, or terrible, depending how you could see it. She was pregnant again. Two months in, in fact. She talked to James about it and begged him that seeing as his best friend was the Godfather of their son, her best friend should be the Godfather of their second. James agreed and told her that seeing as it was so important to her, he would forgive Severus.
She sent him an owl a few months latter, which he recieved. When he opened it his jaw tightened. It read as such:

My Dearest Severus,
I have wonderful news! I am pregnant again! Seven months! I have spoken with James and he agrees, you should be the Godfather. We don't know if it's a boy or a girl yet, but we'll find out in a couple on months! We've told very few people, like our parents, Sirius and Remus.
James forgives you, you know. He begs that you can find it in your heart to forgive him for what he has done to you. He is really very sorry.
Please send word, Severus, I worry about you.
My love, Lily x

Severus wanted to respond, he really did, but he was still bitter that she was having another child by Potter. He hid the letter with the others, in a box under his bed in the Hogs Head where he was staying.
A week latter he overheard part of the prophecy and relayed it to Voldemort. A week after that he was on a hill top begging Dumbledore to hide the Potters in Godericks Hollow. He didn't tell Dumbledore Lily was pregnant, he presumed he already knew.
Now it was two weeks after the Potters had been put into hiding. Severus was sat beside Lucius in front of the glowing fire at Malfoy Manor. Each had a cut glass with a tot of brandy in. A pair of large afghan hounds lounged at their feet. Severus sipped his brandy and secretly sighed to himself.
"I have not had word from our Lord this evening," he said casualy to Lucious.
"Did he not tell you?" said Lucius in his smug, matter-of-fact way.
"I am not sure," snapped Severus back, "it is unlikely he has told you and not me."
"Our Lord has gone to the Potters, he got their location out of their Secret Keeper," replied Lucius, taking another sip of his brandy.
Severus's galss slipped from his fingers and shattered into a million shards of light. The dogs jumped up and growled. He caught himself before he betrayed too much emotion, making his face skilfully blank.
"How long ago did he leave?" he asked in a monotone.
"Twenty minutes, I believe," said Lucius casually, glancing at the mantelpiece clock, "is it important?"
Severus stood, brushed his robes down and strolled from the room, fighting his urge to run. When he reached the hallway he turned and apperated away. When he landed in Godericks Hollow he saw the house that had been the Potters, no longer hidden from view. The top corner of the house was blown apart and there were fires lapping from the down stairs living room window. As he ran towards the little house he put out the fire and pushed his way into the house, through the door which was hanging off its hinges. He coughed against the smoke, but continued onwards into the house. When he reached the bottom of the stairs he saw the body of James Potter, laying on the floor, his eyes staring upwards, unseeing. He passed by him and clambered up the stairs which creaked threateningly beneath his foot-fall.
He reached the landing and walked along it nervously. The sound of an infant crying assaulted his ears. So the Potter boy wasn't dead. Perhaps that meant Lily wasn't, either?
The door to the nursery at the end of the hall was ajar and the big gold letters that spelt out 'Harry' seemed too jolly in the house filled with death. He held his wand tightly in his hand and pushed the door open, heart in his throat and dread heavy in his heart. There she was. Sprawled out on the floor, as beautiful in death as in life. Her lovely bright green eyes looked to the ceiling unseeing, the light that had been behind them was gone. Her swollen belly stretched her top upwards, making her different to the way he remembered her.
He knelt by her side, ignoring the sounds of the screaming Harry in his cot. He put one hand on her forehead, pushing back the hair that was spangled there. He put the other hand on her stomach lightly to steady himself. He took one last look into her lovely, yet lifeless eyes, then closed their lids. Beneath his hand on her belly he felt something. A little bumping kick that was very weak. Blood rushed to his ears and he made a snap decision, knowing that it would be what Lily have wanted.
He pulled back her top to expose her stretched stomach and put his wand tip at the top of her stomach. Carefully, he used a cutting charm and dragged his wand down her belly, cutting open her skin. A little blood trickled from the large wound, but not much, there was no heart to pump it out. Fighting back the tears he felt bubbling in him he reached inside her and cut open her womb. He then reached deeper and pulled the tiny baby out.
It wasn't breathing.
Severus didn't know what to do, he wasn't a mid-wife, he wasn't a paramedic. But he did have a distant memory of reading a book many years ago that had something in it that may have been about child birth.
Holding the baby in one arm he leaped up, grabbing a blanket from Harry's cot and with a flick of his wand it was cleaned of dust. He wrapped the baby in it and cleaned its nose and mouth, then started to rub life into its body. Tears started to fall down his cheeks as he started to feel hopeless. Then, a small squeak.
His tears stopped and he continued to chafe the baby's body until it cried out. He sighed with relief as the baby cried in the blanket. Quickly he cut the umbilical cord and placed it in the cot beside Harry, who had stopped crying now. Severus turned back to Lily, quickly sealing up her stomach and clearing the blood from her clothes and the floor. He replaced her top and looked down on her. This was the Lily he remembered. Still sweet, even in eternal slumber.
He picked up the new born and went to the door way. It would only be a matter of time before the Order would start arriving, he had to get out of here and he couldn't leave the tiny baby, very few people knew about it and something might happen to them. He would have to take it with him. He checked the baby beneath the blankets, looking it over to check it was all right, then looked at Lily.
"It's a girl, Lily, a baby girl. I'll raise her right, I swear to you. She'll want for nothing. I'll protect her and never let her hurt, I'l be there for her," he whispered hoarsely to Lily.
He heard shouts outside in the distance from Muggles as they woke up. Her rushed across the landing, leaving the bemused baby Harry, knowing that someone would come for him soon enough. He carefully went down the creaking stairs and looked down at James. He knelt down decide him for a moment.
"I'm sorry, James," he whispered to the man that had been his rival for so long, "I hope I can forgive you one day, like you forgave me."
He closed James's eyes then stood up, shifting the stirring baby and dissaperating on the spot, just as he heard the roar of a motor bike.

He went to his mothers house, a place he knew that he and the baby would not be found. His mother had recently divorced his father and kicked him out. Now Severus needed her help.
He named her Felicity, meaning 'happy memories', which suited perfectly.
As she grew, her hair came through which was pure white and her eyes darkened to a dark green, like a storm at sea. She didn't cry very much and her eyes held something that made Severus think she knew more than most babies. A bond bound between them as she grew, but she always knew he wasn't her father.
Severus would leave her with his mother during the week and come home at the weekends as often as he could, he had to maintain his job at Hogwarts, he had to provide for Felicity. The first couple of years were hard, Severus went through several enquiries and it made him ache and turned him bitter inside. Dubledore had been very good to him, though, despite the fact that Severus was certain he should be rotting in Azkaban. He knew that was where he was supposed to be, along with all the other Death Eaters. He deserved to die for his betrayal, he knew, but he had to stay alive. He had to keep going, for Felicity. He was her Godfather and nothing would change that.

Felicity showed first magic at the age of one. She had an unusual crying fit for no apparent reason to Severus and his mother. But, then again, they didn't know what had entered the house. All the glass in the house exploded as well as most of the windows in the street.
Thankfully, for Felicity, the Shade that had entered the house retreated quickly at the sudden surge of power that had filled the house. The Shade had been drawn there by something, a strange source of dark energy, but there were many dark things in the Snape house. One thing in particular.

When Felicity was old enough, she was sent to Muggle school. Severus insisted, she had to learn as much as she could before going to Hogwarts. He wanted to give her the sense of reality and the world other than the Magical one which Lily had, something that had made her who she had been. It also meant that he could spend some weekends at Hogwarts.
Felicity learnt a lot and very quickly. She soaked everything up, her desire for knowledge making Severus certain she would be a Ravenclaw, or perhaps a Slytherin.
At the weekends she would read Severus's potion books and started to learn things of the magical world as well.

When she had just turned ten she started to have issues at school. She never really had any friends, people tended to steer clear of her. Her pure white, waist length hair and calculating eyes often scared the other children as well as the strange, cold feeling that sometimes seemed to follow her. Some of the older children had started to pick on her. They locked her in cupboards and called her a freak. But she would never retaliate, never cry. The teachers would find her in the cupboard hours latter when they needed supplies and scolded her for hiding.
That was, until one day when a boy threw a rock at her. She hadn't seen it coming and it hit her on her forehead. It knocked her on her bum and the boy laughed at her nastily, along with the other children.
"You shouldn't laugh at me," she said, standing up, looking at the ground.
"Why's that? Is the tough girl going to cry like a little baby?" jeered the rock-throwing boy.
She looked up at the boy, her eyes darkening to a flat black. She stared at him, her anger boiling over and he started to scream. He clasped his hands to his ears and screamed in an unholy way.
"Stop it! Stop it!" yelled some of the other children.
She closed her eyes and took a breath. The boy stopped screaming and lay on the ground crying. When she opened her eyes again they were their usual dark green. Teachers came running and the blame was placed on her. She was sent home early and told not to come back. She ran to her bedroom and locked herself in with a burst of angry magic and fell onto her bed, crying. Severus couldn't get in, no matter what spells he used. He was secretly proud of her, but mostly he was worried.
She came out in the morning, finding him asleep by her door, his face pained and his breathing laboured. He was having another nightmare.
"Ess!" she said, shaking his shoulder, using her pet name for him, "Ess! Ess!"
He jerked awake and looked around, panicked. Then when he saw her he breathed a sigh of relief and pulled her into his arms.
"Are you all right? The school phoned and- well. What happened?" he asked her.
"One of the boys threw a stone at me," she whispered, stroking his soft black hair, "I got angry and- I don't know, he started to scream and- I forced myself to clam down."
"He threw a stone at you?" Severus demanded, anger in his voice detectable only to her.
"Yes, but I hurt him worse back, but I didn't mean to," she said.
He pulled her to arms length and looked her over, then saw the small cut and large bruise that had formed over her right eye. Then he drew her back into his arms and murmured something he thought she couldn't hear, but she did.
"I'm sorry, Lily, I failed to protect her. It won't happen again."

Felicity wasn't allowed to go back to school after that. She was home tutored by Severus and his mother. They taught her many things and taught her spells, which they encouraged her to try even without a wand. She quickly learnt how to do certain spells without aid of a wand, Severus was extraordinarily proud of her. She was very talented at potions and transfigration as well.
It was a few weeks until her eleventh birthday, the day she would be taken to Hogwarts. She was sat in front of the fire and Severus was in his chair, marking some essays.
"Ess?" she said.
"What is it, Felicity?" he replied, not looking up.
"Why am I going to start Hogwarts two months after the others?"
The scratching of his quill stopped for a moment, then he started to write an even more scathing comment on Weasley's essay.
"Because you're so smart that they couldn't wait to take you next september and they weren't allowed to take you before you turned eleven," he replied.
He looked up and found her facing him, her serious eyes fixed on him. He knew she knew he was lying. It was strange that such a small child could read him so easily.
"Ess, what is it you have night mares about?" she asked suddenly.
He was startled at the change of subject, so told her.
"I dream of the days when I was a child and when I was a Death Eater."
She nodded and looked back at the dancing flames. She knew about her Godfather being a Death Eater, but she was unsure as to what that actually meant, other than they had followed a dark wizard and did terrible things, but as the the nature of these things, she never knew.
"Sometimes you scream," she said softly, watching the pictures in the flames, not seeing the expression on his face.
There was silence for a moment.
"You beg, you beg for Lily not to be dead, too. You beg for James to forgive you. You scream to kill you, too. You say you deserve it."
She turned and looked at him, his face was stony and cold.
"You don't deserve it, Ess, you don't ever deserve it. Who ever James is, I'm sure he'll forgive you. I love you, Ess, forever and always. Don't ever think you deserve to die."
He remained silent, fighting back the tears as the little girl stood, hugged him, then walked to the doorway of the living room.
"I'm going to bed, now, Ess, love you."
Severus smiled weakly at her and she gave him a dazzling smile in return, then scrambled upstairs.