Author's Note: This is a mulitchapter fic I am writing for the TwiKinkFest, there will be cheating and angst (points at the prompt). Don't like don't read. Thanks to Jessypt for being a great beta.

TwiKinkFest Prompt: Cheating. Edward cheats on his wife (Bella) with his sister in law, Leah. I want a build up of UST. Them skirting the line of appropriate that leads to them finally fucking while Bella is passed out in the next room.

Envy is the ulcer of the soul.

Socrates

"There you are," Edward answers the door with a relieved smile that Leah has come to enjoy far more than she should. "I was wondering if I was going to be eating alone tonight."

"Ye of little faith," Leah teases, shutting the door behind her and dumping her overstuffed duffel bag on the entryway floor.

"On the contrary, I have faith in you, Lee," Edward replies, picking up her bag from the floor and turning to head down the narrow hallway. "It's your ability to make it anywhere in a timely manner that I have serious doubts about."

"There was traffic, jerkface," Leah laughs, giving him a playful shove into the kitchen, and stops to inhale the delicious scent of seasoned meat filling the room. "Did you order out?"

Edward tosses her bag down through the doorway that leads to the basement and shakes his head at her. "Traffic? You live less then ten blocks away. I bet you didn't even drive."

"Don't change the subject. Where's that delicious smell coming from?" Leah starts wandering through the kitchen, searching the counter tops for the source of the smell.

"Check the oven," he replies with a chuckle and begins to set the table.

Leah opens the oven door and makes a show of gasping in shock. "Did Bella teleport back to cook for you, or did you cook in some kind of fugue state?"

Edward tosses a cloth napkin at her head. "Stop using big words that you don't understand."

"Fugue state is a rare psychogenic disorder often characterized by reversible amnesia for personal identity," she says in a droning tone and sticks out her tongue at him.

"Show off," he counters and pulls two beers out of the refrigerator.

"The man makes a roast chicken, and he calls me a show off," Leah mutters loudly, carrying the chicken to the table and setting it down with a flourishing wave of her oven mitt covered hands.

"Respect your elders and get me some butter," Edward scolds, setting down a bowl of dinner rolls as he takes a seat at the head of the table.

"Sure, I'd hate for you to break a hip, old man," she says, rolling her eyes at him before turning to head back into the kitchen.

"Watch it! I'm still spry enough to take you," Edward says with a wink and gently slaps her ass.

"Hey!" She yelps and scowls at him, while rubbing her ass.

Leah hopes that her feigned anger is covering up her flushed cheeks and hard nipples. She hates how intensely her body responds to even the smallest touch from him. Edward doesn't understand or even notice the effect he has on her, even when he is just being playful. Leah knows she should ask him to stop, put some physical distance between them to make it easier on her, but she doesn't want to. As pathetic as it is, these small touches and private moments with Edward are like a drug for her. She lives for them, and spends sleepless night replaying them in her mind when they're apart. So, she let's it continue.

When she returns, setting the glass butter dish in front of him and taking her seat beside him, he gives her a warm smile. Leah settles in, spreading her napkin over her lap, and places her hand into his waiting palm. His hand wraps around her fingers, sending a shiver of delight down her spine that she tries to cover with a shake of her head. She looks up to check that he didn't notice her slip, but Edward's eyes are already closed, his lips moving in silent prayer. Her chest tightens a little, and the guilt deepens. Not that she's Catholic or even believes in god, but falling in love with your brother-in-law is wrong, no matter who you pray to.

Leah takes one last glance at the sculpted features of his face before making herself close her eyes to his beauty and pretends to pray. In the silence, left alone with her own thoughts, Leah daydreams about the life she can never have. It's not right. She knows it, but that doesn't stop her from imagining for a few selfish moments.

In her mind she can see them spending every night like this, laughing and together. He would greet her with dinner, just like he did tonight. The house would be warm and filled with the sound of their happiness, and eventually with the sounds of their children's laughter. Edward would be a wonderful father; she knows it. In her mind she can see him cradling a dark-skinned infant in his arms, a proud smile on his face, and an overwhelming feeling of contentment fills her. It's a seductive fantasy that she shouldn't entertain as often as she does, but she can't resist.

"What's that little smile about?" Edward pulls his hand away, and she opens her eyes to see him regarding her with a curious expression.

"Nothing," she says with shrug, mentally scrambling for an answer that will satisfy him, and grasps at the first thing that comes to mind. "I was thinking you were more fun when you used to get high."

"Oh really? I guess I've become a bit of a wet blanket in my old age," he laughs, twin splashes of pink coloring his cheeks as he shakes his head.

"You need to stop saying that," Leah says, suddenly serious and unsure why. "You're only thirty, not a hundred."

"Says the fresh faced twenty-five year old with her whole life ahead of her," he mutters loudly and stabs a piece of chicken with his fork.

"I'm not a kid, jerkface!" she snaps, throwing a piece of her dinner roll at him that he easily deflects with the back of his hand.

"Funny, you still throw like a twelve year old girl," Edward teases and immediately ducks out of the way when Leah throws her butter knife at him.

"I'm going to kick your ass!" Leah charges toward him with her full water glass and manages to cover Edward with most of it, before he tackles her to the floor.

Edward pins her to the floor with his body, holding her wrists and gloats over having captured her so easily, just like he always does. She leans up to try to bite at his face. He jerks back out of her reach, so, she sticks her tongue out instead. He only laughs and shakes his head, spraying her with water. Leah showered him in turn with profanity and thrashes against him, pressing their bodies closer. His shirt is soaking wet, and ice-cold water is seeping through the fabric of her t-shirt, making her nipples hard again.

"Promise me you'll never grow up, Leah." Edward's eyes are bright and the curve of his lips mesmerizing.

"It's too late for that," she replies, breathless and shaken, while she imagines herself closing the distance to kiss him, like she's wanted to do for years.

"Doubt it," Edward says, leaning down to kiss her forehead as she tries to resist moaning out loud.

It's so painful to face. Despite all her yearning and dreams, the truth is it is one sided. Edward still see her as a kid, the little sister, and while he loves her, it's not in the way she wants. She hates how she keeps doing this to herself, keeps taking the table scraps of his affection and dreams of a future that will never be real. Edward isn't her husband, and never will be. No matter how much she loves him.

"Edward," she whispers, looking up into his bright, green eyes, and tries to fight the tears that are threatening to spill.

For a second she wants to end it, to confess her feelings and let the inevitable fall out finally happen. He would let her down gently and tell her how he only sees her as friend and sister. She would cry and eventually let go of him. It's the healthy thing to do, and it terrifies her.

"Wha-" Edward's cut short by the sound of his cell phone buzzing on the dining room table. "Shit, got to get that."

He's gone in a heartbeat, leaving her lying on the floor, a damp, emotional mess. Leah groans and stands up, collecting herself, and turns a calm, curious expression toward him. Edward is leaning against the table, studying his phone with a frown on his face. She wonders if it's the hospital, calling him in for an emergency surgery.

"I thought you weren't on call tonight?" She tries to sound causal, but her voice is still a little shaky.

Luckily, Edward doesn't seem to notice. His eyes never leave his phone, his fingers flying over the keys of his phone while he types a response to what must have been a text message. The look on his face becomes more severe and strained with each passing minute.

"I'm not," he sighs heavily, tucking his phone back into his pocket, but doesn't look up for a moment. "It's Bella."

"Oh," Leah replies, suppressing a cringe and an accompanying pang of guilt. "How's Bells doing?"

"Great, apparently," Edward replies without a hint of enthusiasm in his voice and sits back down at the table to stab at his food with his fork. "She made a big sell and is celebrating with her team."

"Good for her," Leah says, trying to put more effort into sounding genuinely excited and does a better job than Edward.

"Yeah, she's delayed her flight, but she promises she'll be home by Sunday at the latest," he sighs, giving his plate a forlorn look before laying his fork down and pushing back from the table. "Are you ready for desert? I'm ready for dessert."

Edward stands up and walks into the kitchen, not waiting for her to answer. He is obviously upset, his face has shifted through at least a dozen different emotions since Bella texted. Not that he is going talk to Leah about it. Not that he has to; she's been here for enough weekends to know that this isn't the first time Bella has blown Edward off.. He only gets a handful of days off that actually coincide with the free time in her busy schedule. One week a month isn't a lot to ask from your wife of seven years, but over the past year Bella has found ways to whittle it down to a few days.

Leah hates it, even though it gives her more alone time with Edward. She'd rather he be happy instead of brooding over Bella's absence.

"Did you say dessert?" Leah yells after him and tries to summon up a sincere smile. "You, Edward Cullen, made dessert?"

"Not just dessert!" Edward yells back through the doorway and suddenly emerges holding a platter, with a smile on his face. "I made cupcakes with sprinkles."

"Who are you, and what have you done with Edward Cullen?" Leah feigns a suspicious look and crosses her arms over her chest.

"Believe it! Now eat 'em and weep," Edward laughs while he walks into the kitchen, and Leah inwardly sighs in relief.

Seven years ago

In the winter of her senior year, Leah's stepsister, Bella, brought home her new boyfriend to "meet the family." Everyone was excited to meet him, but Leah was annoyed she'd have to play nice with some chump that Bella met in her first year in college. Like the relationship was really going to last.

When Bella walked into the living room with her boyfriend, Leah wasn't sure if she should laugh or feel sorry for the guy. He wasn't unattractive, quite the opposite, but he was wearing a cartoonish Frosty the Snowman sweater that looked like it belonged on a four year old.

"Leah, this is Edward," Bella said with a shy smile, her eyes never leaving her boyfriend's face.

"Nice, sweater," Leah replied, with a limp wave of her hand, ignoring his outstretched hand.

Instead of being offended by Leah's obvious slight, Edward simply smiled a little wider and nodded enthusiastically. "Thanks. It was a present from Bella."

"I couldn't resist when I found out he was a fan of the old Claymation specials," Bella chimed in, wrapping her arms around Edward's waist and giving Leah a look that seemed to say: "Isn't he amazing?"

Leah didn't share her stepsister's enthusiasm in the least, but she did her best not to squash Bella's hopes. Even if the guy looked too handsome and confident to be worth her stepsister's time. After many a failed relationship, Leah had become a believer in the adage that if it looked too good to be true it probably was. She wasn't in the mood to stand around, talking about children's movies, while Bella pawed her douche of a boyfriend, who would probably be old news by New Years.

"Rudolph the Red-Nosed Reindeer was always my favorite," Bella exclaimed with glee and turned to Leah. "What about you, Lee?"

"I hated it! Rudolph cared too much about what other people thought, and that Yukon Cornelius was a dick," Leah snapped, mostly to end the conversation before it got started and to give her a chance to leave.

"Yeah, he was," Edward said, his smile seeming to brighten slightly, and stepped closer to Leah. "I always hated how he picked on Bumble."

Leah immediately felt uncomfortable by Edward's proximity and surprising enthusiasm. "Who the fuck is Bumble?"

"Language, Leah!" Her mother appeared from the kitchen, carrying a tray of cookies and looking the part of the perfect hostess. "Come on everyone. Let's have a seat around the fire."

"He's the Abominable Snowman," Edward replied with a smile and gestured for Leah to take a seat on the couch first.

"Oh, thanks," Leah mumbled and took a seat on the far end of the sofa, feeling awkward.

Edward sat down beside her, with Bella on his other side, and began to continue the conversation, much to Leah's dismay. "I really liked the Frosty Movies, though the song that it's based on is kind of depressing."

"Yeah, it's got to suck to come to life only to melt into a puddle in the spring," Leah commented without much thought and was treated to another brilliant smile from her stepsister's boyfriend.

"Exactly," he said, but before he could continue Bella leaned forward to get Edward's attention.

"Yes, Frosty is great," Bella added. Leah said a silent prayer of thanks for the interruption, until she realized where Bella was going. "Sue, do we still have the old Christmas tapes around?"

Leah suppressed a groan as she realized she was in for a long night of watching shitty holiday specials and old movies. It was one of the things she hated about the holidays, especially since she started spending them with her new stepsister. Bella was all about the cheesiness of the Christmas spirit. She had to do it all, from the decorations, singing carols, and even watching lame Christmas movies. Leah hated all of it.

"I'll go get Charlie," Leah said and tried to get up from the couch, but her mother's hand on her knee stopped her.

"Seth is getting him," Sue replied before returning her attention to Bella.

A few minutes later, Leah's younger brother, Seth, appeared with her stepfather, Charlie, in tow. They both looked about as thrilled as Leah felt, but they all did their duty and played along. The rest of the evening progressed in the usual fashion. They had the required family meal, awkward gift exchange, and mind-numbing but traditional viewing of countless holiday movies.

Eventually, everyone went to bed. Leah waited in her room for a full hour and a half, flipping through her brand new copy of Jane Eyre, a present from Bella. She fingered the smooth pages of the book she hated and wished that just once, Bella would ask what kind of books Leah liked to read, rather than give her ones she liked.

She dropped the book on her nightstand and got up to press her ear to the door. All was silent. She threw her winter coat over her skimpy pajamas, figuring that her Quileute blood would enable her to deal with the damp December night. After grabbing the pouch she had hidden in the back of her closet, she carefully crept from her room and down the back stairs to the kitchen.

She made it out the back door and ducked into the shadows of the garage. As she rounded the corner something moved in the shadows. She froze, panic made her heart pound, and a cold sweat spread across her skin. For a moment she was sure it was Charlie about to bust her.

There was no way she could get away with this; he was going to want to know why she was out here, and she really didn't want to tell him the truth. Luckily, the figure moved out of the shadows, chuckled softly, and stepped forward to reveal himself.

"Beautiful night," Edward said with that same friendly smile and raised his cigarette to his lips.

"Fuck! You scared the living shit out of me!" she hissed and shook herself to get rid of the last of the panic.

"Sorry," he said with a shrug and leaned his back against the garage, exhaling smoke in a long stream.

"Whatever," she grumbled, sitting on the ground, and began fiddling with her pouch. "Why are you out here?"

"Bella hates it," he said, raising the cigarette up. "I'm trying to quit, but..." His voice drifted, and he shrugged again.

"Yeah, she used to nag Charlie about his cigars," she said, rolling her eyes while she pulled out her pipe and loaded the bowl. "Bella has a thing for trying to take care of people even if they don't want it."

"She does it because she cares," he countered, tipping his ash onto the grass.

"Trust me, I know," she sighed, raising her pipe to her lips, but she stopped short to give him a stern look. "Let's make a deal. I don't rat on you, and you don't rat on me, deal?"

Edward's smile turned to a smirk, but he nodded, which was all she cared about. "Deal."

She took a hit off the pipe, loving the itchy burn of the smoke in her lungs. God, she needed this to deal with all the stress. Mom had been riding her ass about picking a college, like she was capable of deciding on important shit while she was trying to keep up with her schoolwork and preparing for the SATs.

Edward was leaning back against the garage wall, exhaling smoke into the chilled night air. He looked so at ease, and she envied him a bit. Things seemed to be easy for him, and damn if he didn't look cool while smoking.

"Can I bum a smoke?" she asked around a lung-full of smoke, trying to keep it from leaking out.

"Depends," Edward replied, kneeling down on the grass next to her, and gave her a sly grin.

She gave him her best bitchy look and leaned back a little. "On what?"

"Are you going to share that?" He casually nodded his head toward her pipe.

She couldn't believe what she was hearing, so much so that she gasped and ended up choking on the smoke in her lungs. The sound she made was this horrible wet squeak that immediately lead into a fit of hacking coughs. She tried to stifle the sound with her hands, while Edward gently patted her back.

After she finally caught her breath, she slapped his hand away and croaked. "Are you fucking with me?"

"No." He sat back on his heels, pulled a small silver flask from his back pocket, and offered it to her. "Wanna sip?"

"Sure." She accepted it and handed him her pipe, while she took a swig of the sour tasting liquor.

"Cheers," he said with a nod and took a hit from her pipe like a seasoned stoner.

Leah couldn't help but stare at him and wonder how the fuck her sweet, shy stepsister had hooked up with this guy. When Bella was in high school she barely spoke to boys. Now, she was bringing home a smoking (in more ways than one) badass that could rock the shit out of a cheesy snowman sweater.

"This is really good," Edward commented, taking a seat on the grass next her, and handed back the pipe.

"Reservation weed is the best in the Northwest," Leah replied, taking another hit.

"I wondered if it was local," he commented, pulling out two new cigarettes and lighting them in his mouth, before passing one to her. Leah took the cigarette cautiously, her suspicion growing and making her suddenly protective of her stepsister. Bella could be annoying, but even Leah couldn't deny she was a good person. She didn't deserve to be jerked around by some con-artist dick playing the part of a nice guy just to get into her panties.

"So, are you serious about this whole deal?" Leah looked at him out of the corner of her eye, while she took a drag off her cigarette.

"Huh?" Edward gave her a confused look and took the pipe from her lap to take another hit.

"This act," Leah said, tugging on his sweater and gesturing to his appearance. "The whole cool sweater guy that meets the parents and shit. Is this legit, or are you playing it up for Bells so you can take her v-card?"

It was Edward's turn to choke and hack. Leah, however, didn't touch him while he wheezed and struggled to catch his breath. She watched him with unflinching focus, wondering if he was feigning the coughing and awkward grin for effect, to get her sympathy. If it was it wasn't going to work. While she may not be best friends with her stepsister, she was family and that meant something to Leah. After a few minutes, he wiped the tears from the corners of his eyes and met Leah's gaze.

"I like her, a lot," he croaked, cleared his throat again.

Leah didn't reply right away. Instead she gave him a hard, penetrating look. He met her gaze with an expression of equal intensity. After few long moments of tense silence, she broke eye contact and lifted her cigarette to her lips. He continued to watch her, his expression softening slightly, while she took a drag on her cigarette and flicked her ash into the dark before finally responding.

"You better," she spoke in a stream of smoke and put out her cigarette on the heel of his shoe. "Charlie will blow your head off if you break her heart."

"I figured as much from the way he glared at me all through dinner," Edward chuckled and wiped at the black smear her cigarette left on the bottom of his shoe.

"I'm not joking," Leah insisted standing up and brushing the grass from her ass. "He'll fucking kill you. Then he'd go to jail, and my mom would be bummed. So, don't fuck it up!"

He put his cigarette between his lips and help up three fingers in a salute. "I swear I will not break her heart, Scouts Honor."

"That is so fucking lame," Leah laughed, gathering her pipe and lighter into her hand, before turning to leave. "Thanks for the smoke."

"Good night," he called after her from the darkness.