I don't own Life with Derek or the characters in this story but this idea was purely my own.

Summery: He never meant for this to happen…he didn't mean to fall for the wrong girl. Maybe she can help him replace her sister.

XXX

He's pumping into her forcefully and without mercy. He can faintly hear her moans of pleasure mixed with pain but he doesn't give her a fucking second thought.

He never meant for this to happen, he never meant to fall for the wrong McDonald sister. He knew what people thought of his relationship with Casey was. No one makes their thoughts a secret anymore.

"There's so much sexual tension between them!"

"I can bet what they do once their parents go to bed!"

"It's a forbidden love!"

What a crock of shit it all was. Unfortunately their words weren't that far off, they just had the wrong girl. He and Casey wouldn't be so forbidden, seeing as how everyone figured it would happen, even their parents thought it and already accepted it. It wouldn't be so accepted though if they knew who he was really after. If only they knew…

He can feel her lips on his neck as she slowly sucks her way down to his hard chest that isn't beating quite as fast as hers is; but that's okay, he's the king of liars and she can't tell the difference anyway. She's so blindsided by her affection for him, her judgment and senses are so fucked up. She was his puppet now and he can make her do anything.

He always knew Casey would end up wanting him. He fucked with her head too much that he actually wanted her to feel this way for him and he has every intention of destroying her because of it; but not right away, he still needed her for now.

Maybe if he closed his eyes hard enough he could picture her body beneath his as he tenderly makes love to her before fucking her into oblivion because he knows she isn't like her sister. She actually deserves to be treated like a Goddess, but he knows of the fire in her just waiting to come out and he plans on being to one to unleash it. Casey deserves to be treated like a whore, because right now that's all she is to him.

He can hear her and he knows she's about to cum. It should make him happy that he can use her whenever the fuck he wants because he basically has his step sister in the palm of his fucking hand, but it did nothing for him. She wasn't the one he wanted, she will always be second best.

He imagines her smiling face, her beautiful pink little lips around his cock sucking him off with that naughty smirk she's thrown his a couple times. He pictures her perfect milky white skin glistening in sweat as she rides him, her still growing tits bouncing faster and faster as she reaches her peck.

He envisions her gorgeous brown eyes looking up at him with such adoration as she tells him she loves him and that's when he finally loses it!

He groans as he blows his load into her, not even caring if she finished or not, before rolling off her. She smiles as she cuddles closer to him and buries her face in his neck.

"Mmm..Love you Derek." Casey whispers gently as she slowly starts to drift into a deep slumber, her face with a small smile as she doesn't have a care in the world. Fuck you Casey.

He looks at her and sees nothing but a distraction, a way for him to get his mind off the one he really wants. Unfortunately it wasn't fucking working! Casey didn't have anything over her sister, Lizzie would always be better.

"I love you Lizzie." He thinks to himself before he moves her away from him. He stares at the ceiling and thinks of ways to finally make Liz his.

TBC? Or The End? I don't know if I want to make this a one shot or a story because either way it could go so I'll leave it up to the reviewers! Please give your opinion!