Loads of people have been asking for a Clary/Isabelle/Sebastian fic so here you go! This one is set in that teleporting house of Sebastian's, Isabelle is living with them instead of Jace here. Hope it's okay for you guys =]

Clary shivered beneath the silk sheet of the king sized bed, the window was wide open and they were in a new location, the outside of which was covered in a blanket of white snow. Getting to her feet, Clary shivered as she walked across to the window and pulled it shut, and only then did she really acknowledge how little clothes she was wearing. When she had stumbled into her room after a night of demon slaying and partying with Isabelle and Sebastian she had been wearing a dress with tights, but now she wore nothing but a black lacy teddy, the thin string of the underwear so uncomfortable she wanted to squirm. She had very few memories of the previous night, but as she examined herself in the mirror and noticed two large love bites on opposite sides of her neck she got one memory return in a blur, she had been so drunk as Isabelle and Sebastian had marked her, she remembered them saying it was so everyone in the club would know she was theirs, not anybody else's to touch. Just as she was about to find something warmer and a lot more concealing to wear, there was a knock on the door. Without even waiting for a reply it was pushed open, Isabelle stood in the doorway. She was wearing high heels and nothing else, but she did it practically all the time so Clary had eventually given up on uncomfortably averting her eyes.

"Oh good, you're awake." Clary's friend said, only she wasn't really her friend anymore, Sebastian had practically brainwashed her so she was no longer Isabelle. "We've been waiting for you."

"Oh sorry, did you want to eat?" Clary asked, feeling stupid as soon as the words were out of her mouth.

"I want to eat you out, that's for sure." Isabelle teased, her voice a simper. She walked further into the room and took Clary's hand in her own, "Come on, Sebastian's been waiting for too long."

She was kind of used to this by now, but still the feeling that Clary got every time she was walking into the scenario of having sex with her brother made her feel sick and she wished she could run away, but even Isabelle was way too strong, Clary would never be able to wriggle out of her grasp. Usually Isabelle didn't join in when Sebastian had sex with Clary, she just watched, but if she wanted to eat Clary out, Sebastian would let her. He loved both Clary and Isabelle, his way of showing it was just very strange. That made Clary shudder slightly, she had never had any experience with another girl, but maybe that would be better than fucking her brother. They reached Sebastian and Isabelle's bedroom and found Sebastian lying back on the bed wearing a shirt and boxers, his arms behind his head.

"You fetched her, Isabelle, good good. Sleep well, Clary?"

Clary glowered towards her older brother, but he just smiled at her, and then made some sort of gesture at Isabelle. Right on cue, Isabelle's hand flew out to grab a lock of Clary's fiery hair and she tugged at it hard. "Answer your brother, Clary."

Trying her best not to try out in pain, Clary gritted her teeth and tried to straighten up despite the hold Izzy had on her, "I've slept better." She managed to get out, and then Isabelle released her hold.

"Come on then, Clary, lie down."

She used to try and resist but she had just been hurt even more when she tried, so now Clary just crawled across the bed and rested back against the pillows, sometimes she could close her eyes and imagine it wasn't happening.

"Sebastian, please can I..?" She heard Isabelle plead, and Sebastian nodded his head.

"Just don't let her come yet, okay my darling?" He told his girlfriend, and then his eyes met Clary's. "You're getting good at this, Clary." He murmured, and then he tilted her face with his hand and bent down to kiss her lips, softly and gently. Part of it made Clary feel sick but when she closed her eyes and imagined it was Jace kissing her it was better. Thanks to Sebastian holding her head she couldn't move it at all to see what Isabelle was doing, but she felt fingers sliding around at the material of her teddy and thong and then the fabric was pulled from her body, and then Izzy's tongue began to lick the folds of her clit and she tried not to moan, but it was hard, it felt so good. Isabelle was better at licking her out than Sebastian, even better than Jace… her tongue moved at different paces, slowly she made a figure of one, then a figure of two, then she quickly darted her tongue around to make the figure of a three, she continued counting until she had gotten to ten and then she started counting down, the whole time Clary's pussy was getting soaked. Her moans were muffled by Sebastian's mouth clamped against her own, and his hands started to stroke across the porcelain of Clary's skin, his fingers hot against her freezing body, he started massaging her now exposed nipples between his fingers so tightly that it hurt, but not so tight that it wasn't also pleasing at the same time. Soon Isabelle's tongue pulled out from inside of Clary.

"She's being good today, Sebastian." She smiled, "I don't even miss having a pet anymore…"

"Quite right, my dearest Isabelle." The white haired boy replied, and then he turned to kiss his girlfriend slowly, the whole time his fingers continued massaging his sister's breasts. Clary whined, her pussy was soaking and she wanted to come but if she did she wouldn't be the only one to be punished, Sebastian would hurt Jace, Simon, Alec, Magnus, Luke, her mother… she had learnt that the hard way. "I'm going to fuck my sister now, okay Izzy?"

Nodding, Isabelle took Sebastian's place rubbing Clary's nipples, but she also started placing kisses across the mounds of flesh there, she kissed her neck too and then her lips hovered by Clary's. "Want to taste yourself, Clary?" She whispered, their mouths so close that Clary's lips tingled, and then Isabelle moved her tongue across Clary's lips before sliding into her mouth, Clary could taste her own juices.

At the same time, she felt kissed being planted at her inner thighs, and then ever so slowly, Sebastian inserted his erect cock into her sopping wet pussy, and he started to move in and out of her almost gracefully.

"Oh sister," he crooned, "Sister mine. We're a family now, aren't we?"

Isabelle took her lips from Clary's and nodded, "You, me and Sebastian, right Clary?"

Clary didn't even nod, she just closed her eyes and forced herself to forget her brother had just came inside of her.

Sorry it's short!