AN: So... JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JALEC JA-

Ahem. Anyway, this is going to be a multi-chaptered fic. I'll leave the rating as T right now, but it might change to M later on. FYI: This is set before City of Bones. No Clary, no Magnus, no Valentine etc. I hope it makes sense :S

Summary: Alec loves Jace, and he's made Isabelle swear not to tell. Jace loves Alec, and he's made Isabelle swear not to tell. So either Isabelle's going to be driven mad by those two idiots or she's going to have to do something about it. But you can't break a Shadowhunter's oath, and there's that little issue of parabatai being forbidden to have a relationship by Clave Law...

Disclaimer: I own nothing. Absolutely nothing.

Flashback: Alec is just under 15, Jace is 14 and Izzy is just over 13

"Why do you always look at Jace like that?" Isabelle asked curiously. They were sitting in a corner of the training room while Jace took his turn being instructed by Hodge on the correct way to handle a seraph blade. Alec had been staring at him, paying rapt attention to every move Jace made. Now Alec was staring at Isabelle, eyes widening slightly.

"Like- like what?" Alec asked nervously. He bit his lip, waiting for an answer, and frowned unhappily. Isabelle frowned back at him.

"I dunno. You're always watching him. It's kinda stalker-ish." Isabelle thought for a moment. "Whenever he's near you, you never pay attention to anyone else. Whenever someone says his name you always start listening to them. It's, like, an obsession or something."

Alec's jaw dropped, and Isabelle was surprised by the look of horror on her brother's face. She had been joking about the obsession part, really. Alec didn't seem to get that. He abruptly stood up and his face cleared of emotion. He looked towards Hodge and, pointedly ignoring Jace, shouted over to him.

"I'm just showing Izzy that book on naming seraph blades. She doesn't quite get it." Hodge nodded and smiled at Isabelle reassuringly.

"Don't worry about it. People rarely understand it first time round," Hodge told her kindly. Isabelle just smiled vaguely, and looked at Alec in confusion. He was already heading towards the door, not checking to see if she was following him. Jace snorted derisively.

"I got it first time. Does that just make me even more awesome than before?" Hodge rolled his eyes and turned back to him. Isabelle hurried out the room after Alec.

"Alec? What is it?" She asked once she was out of earshot. Alec was leaning against the wall, tense and stressed looking. He grabbed his sister's hand and pulled her through the halls of the Institute, not slowing until they'd reached his bedroom. He gently pushed her inside. Alec's room had previously been all-black, like some kind of emo den. Not long ago he'd changed it to white. He'd said it was just time for a change, but they all knew it was because he'd found out that he was scared of spiders and was worried he wouldn't see them against his walls.

Alec dropped Izzy's hand and sat down heavily on his double bed. He put his elbows on his knees and his head in his hands. He drew a shaky breath. He remained silent.

"Alec?" Isabelle asked uncertainly. "Allie?" Alec looked up. Isabelle hadn't called him that in years. Alec looked guiltily at the tears welling up in her eyes, and knew that Isabelle thought she'd done something to make him angry. He sighed and patted the mattress next to him. Izzy walked over slowly and sat beside him.

"Sorry, Iz," Alec told her, taking his younger sister's small hand in his own. "You haven't done anything."

"Then what's wrong?" Isabelle asked, giving Alec's hand a squeeze. She had a concerned frown on her face, making her look much older than thirteen. Much more like their mother, though more caring than Maryse ever managed to look. Alec swallowed the lump in his throat.

"It's Jace."

The words were simple, but they had a huge effect on Alec. He was seized by a sudden panic, as well as relief. He'd said it. He wasn't alone now. He couldn't backtrack what he'd said, not to Isabelle, the most stubborn Shadowhunter ever to walk the face of the Earth. Isabelle frowned deeper.

"What about him? Is it what I said back there?" Isabelle looked at Alec, trying to understand him. Alec wouldn't meet her gaze, and shut his eyes. He screwed up his face as if in pain.

"I... I like him."

"Yeah, so do I. What about him?"

"No, I... I really like him." Alec turned his face away so Isabelle couldn't see his expression. What did he mean? He liked Jace? It sounded like... But...

"But you're a boy. And Jace is a boy," Izzy stated in bewilderment.

"I know, Isabelle." Alec ripped his hand from hers and stood suddenly, moving to his window and staring down at the street several storeys below them. Isabelle watched him, shocked.

"Are you... gay?" Isabelle asked timidly, fearing of Alec's reaction. The word was foreign to her. The only time she'd heard it was during a very awkward 'talk' with her mother. "When a man has romantic feelings towards another man or has a sexual relationship with him." Maryse had said, sounding like she was reciting a textbook. Actually, Izzy was pretty sure her mother was reciting it from somewhere. Other than that, Isabelle had never thought about such an event. Why hadn't she noticed Alec was gay? Alec had always been just... well, Alec. Isabelle considered the weight behind her words. Gay. She repeated the word in her head, but it didn't start to sound any more familiar. Not something she'd associate with Alec, at least.

"Does it matter?" demanded Alec bitterly. "Jace isn't." Alec looked at Isabelle and, in that moment, Izzy decided that she didn't care what Alec was. Alec was taking deep, slow breaths and his eyes were damp. He gritted his teeth and looked out the window again. On an impulse, Isabelle stood and hurried to him. She went around so she was facing Alec and wrapped her arms around him. She leant her head against his chest, him being more than a foot taller than her. Alec let out a muffled sob and hugged Isabelle back. Her heart just about broke. Isabelle's family was her world; when they were hurting, she hurt too.

And right now, she was hurting a lot.

Izzy loosened her arms and pulled away slightly, so she could crane her neck to look at Alec's face. She brought up her hand to wipe away the fallen tears trickling down his face. She considered what to say now, and didn't care that Hodge would be wondering why they were taking so long.

"What are we going to do now?" She asked.

"Nothing." Alec looked her right in the eye, shaking his head. "Absolutely nothing. You can't tell him about this, Iz."

Isabelle chewed at her lip. "Okay," she lied. Alec frowned seriously. For someone who was a terrible liar himself, he could sure pick out someone lying from a mile away.

"No, Isabelle, you don't get it," Alec said pleadingly. "The Clave..." Alec faltered and swallowed nervously. He let Izzy go but she didn't move away. Alec sighed. "The Clave doesn't like it. They strip your Marks and throw you out to live like a mundie. I'd never see you again, any of you. What's the point?"

"But maybe-"

"Isabelle, there are no buts. Trust me; I've researched it and everything. Even if Jace did like me back, there's nothing we could do about it." Alec met Isabelle's eyes and knew that she was still contemplating that there must be some way to talk to Jace. Alec bit his lip, panicking. "Izzy, please. Swear it."

"Mom says I'm too young to Swear anything," Izzy reminded him, a little scared. Alec smiled despite himself.

"Since when have you listened to anything Mom's ever said?"

Isabelle smiled back ruefully. She took a deep breath and said, "Okay. What do I have to do?"

"You need to say 'I swear on the Angel never to tell Jace what you told me'."

"What? Is that it?" Isabelle frowned, feeling a bit disappointed. Maryse had always made out Oaths to be a big deal and really 'dangerous'. Alec nodded.

"Yeah. When they say it's dangerous, they're usually talking about what happens when you break them." Izzy shivered at Alec's dark tone, even though he was only teasing her.

"So do I just repeat that?"

"Yep. No, wait! Add in Mom and Dad too." Alec waited for her to speak.

"Right." Isabelle cleared her throat and looked Alec right in the eye. "I swear on the Angel never to tell Jace, Mom or Dad what you told me," she said clearly.

They both waited for a minute before Isabelle broke the silence. "Did it work?" She was expecting something to happen. She didn't know what, just something.

"Yeah, that's it." Once it was done, Alec looked guilty. "I shouldn't have done that," he said miserably, biting his lip yet again. "I mean it Izzy, if you tell them-"

"Alec, I promise I'll never tell them," Isabelle said earnestly. "Promise."

Her brother smiled at her, the worry not quite disappearing from his eyes. He glanced at his watch and winced. "Crap. We need to get back." Just as he made to turn around, Isabelle caught his arm.

"Wait. Come here." She pulled him into his bathroom and turned on the cold water. "You're all blotchy."

"Ah, thanks." Alec stuck his hand in the water and dabbed it over his face until the red started to disappear.

"Ready?" Asked Isabelle when Alec turned off the tap.

"Yeah." Alec smiled at her gratefully before leading her back down to the training room. Jace was slouched on the bench in the corner with a bored look on his face. When he looked up and saw the two of them, his face lit up. Isabelle heard Alec catch his breath and glanced at him from the corner of her eye, to see him smiling gently, staring straight back at Jace. Isabelle smiled sadly and wondered if Alec even realised what he was doing.