Title: The half-blood princess

Summary: The Snape siblings loved each other to no end; they simply were in the habit of snapping first and apologizing later. AU story. No siblings incest. Rated M just to be safe.

Warnings: mentions of abuse and violence. I don't think it is very graphic though. I'll rate it M, just to be safe.

I don't own Harry Potter. The only character I own is my OC, Severus's sister.

Chapter 1: The oath

Livia Eileen Snape was sitting on her bed. Her little fingers curled around a timeworn ragdoll. Tears were starting to form in her deep black eyes. Her thin lips were quivering, threatening to cry anytime now. She could hear glasses breaking. Unfortunately, it wasn't an uncommon sound at the Snapes. When a painful cry from her mother was heard, the infant hugged her doll close to her chest and shut her eyes, finally releasing some silent tears which fell down her pale cheeks.

"Liv! Here you are!" a boyish voice exclaimed relieved.

It belonged to Severus Tobias Snape. He had been looking for her since the moment Mr. and Mrs. Snape began their usual dispute which would likely turn into a violent madness of fisticuffs and kicks. The eight-year-old always dragged his sister upstairs in a poor attempt to pretend that nothing was wrong, even though the boy bet that the entire neighborhood could catch an earful of what was going on at their home. Severus hurried to Livia and sat next to her. The girl instantly threw away her ragdoll without caring where it landed and hugged him close. Her hold was incredibly strong for a four-year-old. She hid her hooked nose in his shoulder as a weep escaped her throat.

Severus was shocked. At first, he didn't know how to react. Livia was acting so out of character in that moment… She was his annoying little sister who'd ask to make puzzles with him and to play hide and seek around the house. She always wore a bright and pure smile on her face that was able to light up the dark home they had to live in. So yes, feeling her thin arms binding his waist bitingly while she cried wasn't a sight his brother was used to witnessing.

"Liv, what's wrong?"

"Daddy's mean," she babbled without loosening her grip or looking at him. "I see other daddies in the park, and they ain't like Daddy. Daddy's mean. He never plays with us and he treats Mama badly."

Severus gulped at her words. He had always got the impression that Livia was too young to fathom the toxic relationship their parents had. Truth be told, he didn't fully understand it either. Yet, his sister seemed to distinguish that something was off in their broken home. And she was right. The boy hugged the girl closer as louder yells from their parents were heard.

"Father isn't mean, Liv," he murmured in her ear. He didn't want his sister to lose the innocent smile she always wore. It was one of the few things that made his life better. If he had to lie to keep her cheerful spirit on, then he'd do just that.

Nevertheless, the kid shook her head and repeated, "He is. Mama's crying."

It was true, amongst the hustle of the broken glasses and the mad shrieks, it was clear to hear some sobs. Severus couldn't stand the sound. He could do nothing but caress her back in an awkward yet reassuring motion.

"Why does this happen to us? Am I mean? You say I'm annowing when I ask you to draw with me."

The boy sighed and assured her while trying to articulate clearly the word she had mispronounced, "No, Liv. You can sometimes be annoying, but you aren't mean."

He kept patting her hair gently, letting his fingers curl through her light brown locks, the same shade of their father, in contrast to the black hair he had inherited from their mother. They heard as Tobias hit his wife repeatedly, until she begged for him to stop.

Silence invaded the house, but it didn't carry a peaceful atmosphere with it. It left their home shattered, ruined. Severus sighed, knowing that at least for some time, their parents wouldn't fight anymore. The child pushed his sister away gently. She had some tears in her face, but the boy dried them quickly. While his thumbs were stroking her high cheekbones, he made a vow: he'd do anything to protect his little sis. She was still weeping from time to time, but since quietness took over their home, her cries had started to dwindle.

"One day we'll get out of here, Liv. We'll receive our Hogwarts's letters and go far away to learn magic! You'll see! We'll be safe there and we'll learn how to brew potions and cast spells and even fly on a broomstick!"

The four-year-old let out a high-pitched giggle and wondered with sparkling eyes, "Magic? Like Mama?"

Her expression had turned from sadness to enthusiasm in a fraction of a second, and a soft chuckle escaped Severus's throat.

"Yes. Like her. I will become a Potions Master, I am sure of it."

Livia wrinkled her nose in disgust and pouted, "Poshions? They make fumes! And they are yucky!"

Severus shook her head. After all, he couldn't expect that his sister would understand that potions went beyond making fumes and yucky things, as she put it.

"Sev! Come and draw with me!"

At her lively expression, he just couldn't say no to her, especially after the break-down she had had upon their parents' brawl. He found himself taking out some papers and a few thick crayons that needed to be sharpened to actually paint. After sharpening all the colors, they lay on the floor and let their hands move freely to sketch different pictures. Severus was so absorbed that he was slightly biting his tongue, whose tip was poking out a side of his mouth. He really wasn't paying attention to Livia's endless rambling. She usually prattled on and on about nonsense things while they drew. An hour later, the eight-year-old made the last retouch and smiled proudly at his creation. He had painted a castle. There was a boy dressed in a uniform flying on a broomstick and next to him, there was a little girl in the same clothes, also flying a broom. When Livia saw it, she burst into laughter.

"What's so funny?"

"Sev! What's that?" she inquired with a light-hearted giggle as she pointed to his drawing.

Severus felt the heat rise to his cheeks in embarrassment. His little sister was making fun of his drawing skills. How very humiliating.

"It's Hogwarts. And we are flying on broomsticks," he retorted indignantly.

The lass took the paper from his hands brusquely and inspected it attentively for a few seconds. She pointed at their flying figures and mumbled, "I need to teach you how to draw! The broomticks look like flowers!"

"They are called broomSticks, and they don't look like flowers! I worked hard on them!" he complained with a scowl, feeling indignant.

Livia simply stuck out her tongue at him, mocking him further. Severus was losing his patience. He was about to snap at the kid when something caught his eye: Livia's drawing. It was easy to tell that it represented Severus working on some potions. She had exaggerated the fumes, which were invading the paper with endless messy multicolored spirals. The table, where the cauldron was placed on, appeared to be flying as she had forgotten to actually color the floor. She had tried to draw Severus poking his tongue out in concentration the same way he had been doing before. His hands were way bigger than they should be and they looked like simple circles with some lines to simulate the fingers. His hooked nose was overly large for the face she had drawn and his eyes were two tiny black points. Surely, proportions weren't her thing, but Severus couldn't blame her. He didn't even mind it. The simple fact that she had taken the time to draw him moved him. The frustration he had felt earlier trailed off in a matter of seconds and was replaced by a warm and fuzzy feeling.

Yes, Livia Eileen Snape could be annoying to no end. She was by his side 24/7. The child imitated him all day long. She even mimicked his intonation, his words and his gestures. Livia had already mastered raising an eyebrow and pulling a sneer on her face in the same fashion Severus did, and he was sure that she only did that to taunt him. If he said to his mother that he was going to the park, his sister followed him. If he decided to read, she took a book and, despite not understanding a single word, she kept turning pages at the same pace of her brother. If he offered to lend a hand to Eileen and sweep the floor, Livia rushed to get the broom to sweep it herself in a poor attempt to help, even though the object was way too heavy for her and she really didn't clean well. If possible, Severus got the impression that she spread the rubbish even more around the house. He had to sweep deeper after her, and that irritated him desperately. At heart, he knew that his sister adored him and looked up to him. And it was at times like these, as when Severus saw askance her drawing of him, that he understood that he wouldn't have it any other way. Severus loved her, as incredibly unimaginably infuriating as she could be.