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The Thread that was Buried

Summary:

Charles remembers the first time he saw her: clothes too big, eyes too hollow, clutching their father's hand beneath their mother’s disapproving glare.

“Charles, this is your older sister,” his father said, his mother bristled with barely concealed anger at the sight of an illegitimate child, a bastard.

He was five. He only heard “sister”—and reached for her hand with joy.

She died two years later. Crushed by a car, gone, and buried - forgotten by the world. And Charles never quite stopped blaming himself. Meeting Raven was like salvation.

But the dead don’t always stay buried. Unbeknownst to him, she clawed her way out of the grave, and survived—shaped by war, shadows, and the gift she never got to name. While Charles dreams of building a better world, Xylia walks the one that's already burning.

And when their paths cross again, nothing will be as it was.

-- basically Charles had an older half sister, she died and then came back to save him (plot still follows X-Men: First Class closely)

Notes:

Hi there! I haven't written for X Men fandom for ages (couple of years), and I have been really out of touch, only having read some a handful of fanfics for the first time in years. I know OCs can be annoying for people so I have stuck to the film plot a lot but with some extra background. Cherik will come in the later chapters, I promise. Unfortunately, the writing quality is not as great as I wanted but I've got exams around the corner but this story idea would not leave me alone - I had to get it out. I have an old work that also has Charles with an older sister, just to let you know, this is not the same! Enough about me then, enjoy!

Chapter 1: Unwanted Child

Notes:

Xylia is Charles' illegitimate older sister, if it isn't clear. Don't worry it gets explained in the chapter. Don't let it throw you off!

(See the end of the chapter for more notes.)

Chapter Text

The rain had begun early—soft at first, like the house was sighing—but by nightfall it lashed the windows with violent fury. Wind howled through the eaves of the Xavier estate. Thunder cracked, shaking the floorboards beneath Xylia's narrow bed.

She didn’t flinch. She was used to noise.

Down the hall, behind thick oak doors and under velvet covers, six-year-old Charles likely slept soundly. Storms frightened him, though he never said it aloud. When he was smaller, he’d sneak into her room, curling against her side like a kitten. He hadn’t done that in over a year. He claimed he was too big now. She missed him anyway.

The manor was cold and cavernous, filled with echoing footsteps and locked doors. It wasn’t a home—it was a monument to reputation. Certainly not a place to raise children. Especially not unwanted ones.

Xylia sat upright in her tiny third-floor room, knees drawn to her chest, the threadbare blanket falling from her shoulder. No lace curtains, no fireplace, no toys. She looked nothing like Sharon Xavier, who embodied aristocratic poise and icy precision. No—Xylia took after Brian. Same deep-set eyes and long lashes, the same sharp cheekbones. Her resemblance to him was the one thing Sharon hated most.

To Sharon, Xylia was a constant reminder of betrayal—of how even her husband could be swayed. The other women of her social circle didn’t speak openly, but their silences were sharpened with judgment. At luncheons, a raised brow. At galas, a too-sweet smile. Xylia was the stain on her pedigree, the whisper in the drawing rooms: the bastard child under her roof.

And Xylia’s very being—not only her existence but the way she mirrored Brian so plainly—set Sharon’s nerves alight. The curve of her mouth, the stubborn line of her jaw, even her voice held echoes of his. But worse still: she was a girl. A girl who could never be an heir. Who had no place in the legacy Sharon so carefully curated. Charles would be the future. Not Xylia.

She remembered the day Brian brought her—eleven years old, half-frozen, gripping a cracked plastic swan and a bent photograph. Her birth mother had died of fever, her body still warm in the bed when Xylia found her. That woman had never been kind. Her eyes were sharp, her hand sharper, always cursing Brian's name, calling Xylia the ruin of her life. Brian had never visited. Only sent cheques. When the illness came, the money wasn't enough.

Desperate and shaking, Xylia had written a letter. Misspelled, stained, begging for help.

Weeks later, he came.

And he took her.

At first, Brian tried. There were moments. Warmth. He read her Jules Verne by the fire. He bought her gloves in the winter, silk-lined. He helped her name the sparrows nesting outside her window. But Sharon's presence was a cold tide that eventually swallowed all softness. Her words wore him down. Each time Sharon stared too long, too cold, he would retreat further.

But in those first months, when hope was still alive, there were moments of joy. Charles, only four at the time, had peered at her from behind a velvet armchair. He had giggled when she poked her tongue out. He dragged her into hiding places—the butler’s pantry, under staircases—and together they plotted war against the house staff. They tied the butler’s shoes together with ribbons. They filled Sharon’s prized garden shoes with cold porridge. They whispered stories beneath the bedsheets, made forts from pillows, and lit stolen candles to read pirate tales late into the night.

Charles had never said it in front of anyone else, but in those secret places, he called her sister. Softly. Like a secret too precious for the world.

Sharon hated it. Hated how Charles clung to her. Hated how Brian's eyes softened when he saw them curled together. She scolded the staff if they let Xylia near the drawing room. She removed her from photos. She once slapped Xylia’s face so hard her vision blurred, because Charles called her “sister” at dinner.

The voices began in the second year.

It started slowly. Just flickers of emotions that weren’t hers. Waves of sorrow that came out of nowhere, moments of dread when no danger loomed. She chalked it up to the loneliness at first. To grief. To being eleven, twelve, in a house that didn’t want her.

Then came the thoughts.

They weren’t loud. They weren’t even clear. But they weren’t hers. And some part of her—buried deep and frightened—knew it.

She sat Brian down one evening. He was in the library, staring absently at the fire, a brandy untouched in his hand. She took a deep breath and stood before him, heart pounding in her throat.

“I think there’s something wrong with me,” she whispered.

He blinked, startled out of his haze. “What do you mean?”

“I hear things. Thoughts. Feelings. Sometimes… sometimes I know what someone’s going to say before they say it. I don’t mean to, but… it’s like it’s in my head. Like I’m not alone in there.”

Brian went very still. For a long time, he didn’t speak. Then he rose, slowly, and placed a hand on her shoulder.

“You’re just... sensitive,” he said. But his voice wavered.

“I’m not lying,” she insisted.

“I know.” His fingers tensed. “Just... don’t mention it to your stepmother.”

But it was already too late. Sharon had overheard. She stood in the hallway like a statue carved from ice, eyes wide, mouth thin. Xylia scrambled to explain herself, but Sharon strode in. The slap rang out before she could finish. Her lip split.

“Lies,” Sharon hissed. “Filth. Attention-seeking mongrel.”

That night, she and Brian argued. Not a cold debate—this was venom and ice and old wounds flung like daggers.

“She’s dangerous, Brian. I will not have her corrupting Charles with madness,” Sharon hissed, arms folded tightly across her chest.

“She’s a child,” Brian snapped. “She’s frightened, and you’ve given her no comfort. She’s not dangerous—she’s just different. And we should be helping her understand it.”

Sharon’s laugh was brittle. “Of course you’d say that. Anything to wash your guilt, isn’t it? You let that woman rot in some hovel, and now you want to play hero?”

Brian flinched.

“She doesn’t belong here. And if you’d had any decency, you’d have left her where you found her. But no—you had to bring your shame home and drop it at my feet.”

“She is not my shame,” Brian growled.

“She is your betrayal,” Sharon spat. “And don’t think I don’t see how she looks at you. How much she looks like you. Every time I see her, I see what you did. What you ruined.”

Brian’s voice broke. “She’s not the one who ruined anything. You’ve never given her a chance.”

“And you’ve given her everything but a name. You keep her upstairs like a ghost, let her wear my son’s old cast-offs, and call that kindness. You let me strike her, and say nothing.”

Brian’s shoulders sagged. “I didn’t want this life for her.”

“Then send her away. Before she burns the rest of it down.”

And he agreed. Not out of malice. Out of exhaustion.

Out of cowardice.


It was decided within a week.

No letters. No ceremony. Just a folded letter from a school she’d never heard of. A place for ‘exceptional children,’ they said. Far away, and quiet. Brian wouldn’t meet her eyes when he handed her the papers. Xylia didn’t cry. She nodded like she understood.

In truth, she didn’t.

She didn’t know what she’d done wrong—only that she had been caught being strange in a house that demanded quiet perfection. That she didn’t belong, and now, finally, it was being made official. She packed slowly over several days. There wasn’t much to take: a few books Brian had given her, the cracked plastic swan, a wool jumper Charles had insisted she keep because it “smelled like safe,” and a battered suitcase that still smelled faintly of her mother’s old flat. Sharon didn’t speak to her. The staff avoided her gaze.

Charles was the only one who noticed something was wrong.

“Why are you packing?” he asked one afternoon, padding into her room in his stockinged feet. She froze, halfway through folding a nightdress. “Are we going somewhere?”

She smiled faintly. “I am.”

His face twisted. “Without me?”

Xylia sat on the edge of the bed, patting the spot beside her. Charles climbed up, legs swinging.

“It’s a school,” she said gently. “A special one. They think I might do better there.”

“But you hate school.”

She laughed, a brittle sound. “This one might be different.”

Charles frowned. “When are you coming back?”

There it was—the question she had no answer for.

She reached into her pocket and pulled out the swan. It was worn now, faded and cracked, but still whole. She pressed it into his palm.

“Keep this for me,” she said. “So you remember I promised.”

His fingers curled tight around it like a lifeline, eyes wide. “You’re really going.”

“I have to.”

He didn’t say anything. Just leaned into her side and wrapped his arms around her waist. She held him as tightly as she dared.

That night, as the house slept, Xylia passed the drawing room again. Through the thin crack in the door, the voices returned—hushed but cutting.

“She barely eats,” Brian was saying. “She’s so quiet now. It’s like she’s already gone.”

“And good riddance,” Sharon said coldly. “The moment she steps off this estate, we can begin again.”

“You make it sound like she’s a disease.”

“She is. A symptom of your betrayal. And I’ve been living with it for years.”

There was a long silence. Then:

“Do you remember what she looked like when I first brought her?”

Sharon laughed. “Half-drowned. Filthy. Holding that ridiculous toy. I thought she was a stray.”

Brian sighed. “She was a child. Mine.”

“She’s not mine. And she’s not fit for this life.”

“I don’t want her to live like this either,” Brian said softly, pain in his voice. “Some days I think… if she hadn’t survived…”

Xylia didn’t wait to hear the rest. The crack in her chest, long splintered, finally gave way. There would be no going back from this.

She turned. Walked.

Not up the stairs. Not to her room. Not to Charles, who slept curled around the promise she’d left in his palm.

She walked straight to the front door.

The corridor blurred past her—walls she’d learned to keep her head low within, portraits she’d memorized to avoid looking at Sharon too long. The wind outside rattled the windows, the house groaning under the weight of the storm, as if it, too, knew something terrible was about to happen.

She stepped outside.

The rain hit like ice. It soaked her to the bone in seconds, clinging to her nightdress, tangling her hair across her face. The gravel bit into her bare feet, sharp and cold. She welcomed the sting.

At first, she walked.

Then—she ran.

Tears blurred her vision as her lungs heaved. Not from the cold, not from the pain in her soles—this was something deeper. She’d always known she wasn’t loved, but somewhere in the cobwebbed corners of her heart she’d still held on to the hope that maybe, just maybe, Brian cared. That maybe she could still be something.

But now—

She’d heard the truth in his voice. The tired resignation. The quiet confession.

If she hadn’t survived…

Inside her skull, the voices shrieked. The storm around her was loud, but this was worse. Sharon’s satisfaction pulsed like poison. Brian’s guilt tore like glass. Servants asleep behind windows. A house unaware—or uncaring—that one of its children had been broken for the last time.

She wasn’t sure where the driveway ended. Her feet just kept moving.

Then—

Headlights.

Blinding. Sudden.

The staff car rounded the bend too fast in the slick rain, its beams slicing through the dark.

Xylia froze.

There wasn’t time to scream.

There was only the sound of tires locking, rubber scraping gravel—

Impact.

Her body lifted from the ground in a quiet arc. No thrashing, no flailing. She hit the earth like a dropped doll—limbs bent in ways they shouldn’t. Her head struck stone with a sickening crack.

And everything went still.


It was the butler who saw it first. He dropped his tray.

The tray shattered.

The sound brought others running.

Brian appeared barefoot, shirt half-buttoned, eyes wide with confusion—until he saw the shape at the edge of the drive.

At first, he didn’t understand.

Then he did.

He ran—through puddles, through gravel, falling to his knees in the mud beside her. The blazer was off his shoulders before he’d finished breathing her name.

“Xylia—”

She wasn’t moving. Blood trickled from her temple. One arm bent behind her. Her hair matted with dirt.

He covered her with the jacket anyway. His hands shook.

Behind him, Sharon stopped short. For the first time in years, her mask cracked. There was no room for elegance here. No perfect poise. She staggered, hand flying to her mouth. She made a sound—choked, guttural. This wasn’t the quiet end she’d wished for. This wasn’t disappearance or dignity.

This was carnage.

A child, barely more than a girl, broken open on the driveway.

Her stomach turned. She backed away—into the hedges, into shadow—as if the scene might swallow her too.

Brian stayed kneeling, mumbling half-prayers and half-denials, like words could reverse time. His voice broke halfway through her name.

Then—

“Xylia?”

A small voice. Barely more than a breath.

Brian turned.

Charles stood in the open doorway, barefoot like her, holding the swan. The storm howled around him. The wind whipped his curls. He looked even younger in that moment—fragile and blinking.

He took a step. Then another.

Brian stood too late.

“No—Charles, don’t—”

But the boy ducked under his arms.

He ran.

The sight hit him like a slap.

The body. The blood. The twisted limbs.

He dropped to his knees beside her, shaking her arm.

“Xylia? Wake up.”

She didn’t move.

“Sister?”

His voice cracked.

He shook harder. “You said you’d come back. You gave me the swan. You promised.

Brian tried to reach him, but Charles screamed, clutching her.

“She’s cold—she’s cold—she’s not waking up—!”

He screamed until his voice gave out. Then, sobbing, he collapsed onto her. Brian pulled him gently back. Charles fainted against his shoulder.

And in the space of that storm, nothing else moved.

Notes:

I hope you enjoyed this chapter - this kind of writing is new for me as well, I wanted to capture the feeling of what it could have been like at that time. The Xaviers are old money, socialites, aristocrats, and in the late 1930s and early 1940s, not only did women and girls have little value and looked down upon, for upper class nobility like the Xaviers, blood was so important so of couse Sharon would hate an illegitimate child. As I did some background reading on how upper class functioned in the US back then I was so saddened and probably didn't do it justice. Do let me know how you found it though! I love your comments, always!