A/N: I got the idea for this story while listening to the song "I know you" by Lori McKenna but it is not really a songfic cause the lyrics don't really fit. Anyway, it is my first stab at a multi-chapter fic and only my second story overall, so please R&R!

I Know You

Chapter 1: Realization

"Der-EK!!" the familiar shriek rang through the McDonald-Venturi household as Casey stormed down the stairs in her pajamas holding something that looked like confetti.

Casey stomped into the kitchen where her step-brother was sitting at the counter eating his cereal. When she reached him she threw the paper shreds at him angrily and they stuck at odd angles in his messy chestnut hair. Un-phased, he simply turned around and smiled innocently at the fuming girl in front of him.

"What could I have possibly done this time, my dear stepsister?" he asked.

"UH! You KNOW what you did, Derek. You shredded my extra credit history report! I worked for hours on it and know it is confetti! Why would you do that?" she asked with a twinge of hurt in her face.

Derek just rolled his eyes. "Oh please, Case. First of all, I did it because I was bored and I just found my scissors. And second, I think I did you a favor. I know for a fact that you already have a ninety-seven percent in that class and if you turned in that report when you didn't even need the extra-credit you will never escape your grade-grubber keener reputation."

Casey thought for a second, obviously torn between her annoyance and acceptance of his words. After all, what he said was true, but she was still mad at him for ruining her hard work.

"Whatever, don't act like you actually did it to help me, you were just trying to bother me," she said finally.

"Hey, believe whatever you want. Just remember to thank me when you aren't at the complete bottom of the social ladder. Although really, I can only do so much for someone so naturally prone to being un-cool." Derek put his empty bowl in the sink and started heading for the door. Only then did Casey notice he was already fully dressed and ready for school.

"Derek, why are you leaving so early?" she asked.

"What do you mean early?" he said mischievously before continuing. "Oh, that's right; I forgot that I set you clock back half an hour. Well, you better get ready quick, school starts in ten minutes. Bye, Case!"

"UGH!" she screamed to no one, since he had already left the house. She ran upstairs and hurriedly got dressed and ready, only to realize that Derek had taken the car. Both George and Nora were gone and Emily most likely would have left already, so Casey had no choice but to walk, scratch that, run to school.

Somehow she arrived only a few minutes late, and because of her disheveled appearance and out-of-breath explanations she even avoided detention. But she was absolutely livid at Derek who was laughing at her from the back of the class as she ran in. She took her seat near the front with only one thing on her mind: revenge.

Her opportunity was practically thrown in her lap that weekend. Sally was over as usual hanging out. When Derek left the room for a minute to get a snack, she pulled Casey aside.

"What's up, Sally?" Casey asked.

"I wanted to talk to you about Derek," she said seriously, glancing back towards the kitchen to make sure he wasn't around. "Listen, I don't want him to overhear so do you mind coming by Smelly Nelly's tonight since he is not working?"

"Um, Sally, I don't really think that is a good idea. I mean, Derek and I kind of have this agreement where we don't get involved in each other's personal lives…" she trailed off uncertainly, remembering the pranks he had pulled on her earlier in the week. "You know what; on second thought I think it should be fine. Meet you there tonight." Casey said devilishly.

"Thank you so much Casey, I really need someone level-headed to talk to!" Sally said sweetly, almost making Casey feel guilty for the devilish plan forming in her mind.

Casey strolled into Smelly Nelly's later that night feeling better than she had all week. After everything Derek had pulled lately she was about to have a serious conversation with his girlfriend specifically about him. It was her perfect opportunity to tell Sally exactly the kind of guy Derek really was. This was going to be good.

"Hey Case," Sally said sitting into the booth opposite her, "I am on break. Thanks for coming, I just figured since you are Derek's sister you must know him pretty well."

"I am not his sister," she said, probably too strongly, "but yeah, I guess I must after living with him."

"Right…well, anyway, we have been dating for awhile now and I know he likes me but sometimes I am just not sure how he actually feels about me, you know?" she looked contemplative for a moment. "I just wish he would take some things more seriously. And it's also been bothering me how he treats you and other people, I mean, I want to believe he is really a good guy but it seems like I have to force him to be nice sometimes, like at Marti's birthday." She sighed and looked at Casey pleadingly.

Casey looked at Sally and thought about what she was saying. She thought about what she had planned, remembered all the mean things Derek had done to her in the past and was almost ready to tell Sally all of the bad things about him.

But then she started to think about the way Derek was when he was with Sally. She thought of how happy she made him, and of the nice things Derek had done for her in the past. No, he really was a good guy at heart she knew, and she just couldn't find it in hers to ruin his relationship. So she tried to put her animosity behind her and told Sally the truth about Derek.

"Sally, don't worry. I know for a fact that Derek likes you more than he has ever liked anyone. He has trouble expressing his feelings in words but he shows them in other ways. The way he looks at you like no one else is around, the way he is happier when you are with him, the fact that when you talk he actually listens…" Casey trailed off thinking of Derek, almost forgetting her point.

"Ahem. As far as taking things more seriously, it is hard for him because he is so used to putting up this cool guy front that it is hard for him to let his defenses down so he makes jokes and is immature so he won't have to deal with real life. He is just scared, really. And honestly, I know it seems like I would be the last person to say this but he really IS a decent guy. He pulls his little pranks but he would never actually hurt anyone intentionally, and when worst comes to worst he is always there for the people he cares about," Casey finished, a little surprised that she meant everything she said.

Sally looked intensely relieved. "Wow Casey, I half expected for you to tell me what a horrible guy he was. But what you said makes a lot of sense, I guess I will just have to let Derek take his time and show me how he feels in his own way. Thanks so much, how did you know all of that?" she asked.

Casey was now feeling horrible, a new realization gnawing at the back of her mind. "Like you said, I know him." She said sadly, still pushing back the thought that was trying to creep into her head.

"Is that all you wanted to talk about 'cause I should really get home," she said.

Sally was by now positively beaming, all of her doubts about her boyfriend having been erased. So she told Casey goodbye and returned to work. Casey walked out of the restaurant in a daze. Finally she was alone in her car and it was then that she let her full realization hit her. Something she had realized while she was talking to Sally, although she suspected she had known it for some time: she had fallen for her stepbrother.

A/N: This first chapter turned out differently than I expected, but I suppose the story has a mind of its own. Please, please review! I will get the next chapter up soon so any suggestions you have for my writing would be great! Thanks!