He had won and she had lost and that was the bottom line. Initially it had just been an argument between siblings but it ultimately turned into a bet over their grade point averages. His sister bet that she would end up with the higher GPA and she had lost, 3.9 to 3.87... it was close but still she had lost.

When they had first argued over their GPA's it had just been for fun then his sister taunted him about her being smarter and Mark caved in and agreed to the bet. Mark had at first been hesitant to agree with his sister because she was so damned smart but when she had said that she would do 'anything' he wanted, assuming he won of course, he had smiled and then agreed and they sat down and hammered out the details. Mark still remembered the conversation like it was yesterday although it had been almost nine months ago...

"I'll tell you something Mr. Jockstrap," Caroline said to her brother, "I'll be standing behind the podium as the class valedictorian and you'll be listening to my speech with the rest of the crowd out in the audience."

"Bull, I can beat you in a heartbeat!" He didn't really believe that but he couldn't back down now!

"Really? Well I'll tell you what brother; if you beat me I'll do anything you want."

Mark cocked his head and thought about her offer. "Hummm... anything... alright sis what exactly are you offering?"

Caroline was positive that she was going to win so she offered what she knew would intrigue him the most. "I'll put myself on the line here Mark; I'll do anything your little perverted mind can conjure up short of having sex with you although I'll bet that already crossed your dirty little mind."

It had, but Mark shot right back with his counter offer. "Alright smart ass, no sex but here's my deal, take it or leave it. If I win I want you to give me a hand job and I want you to do it with nothing on but your bra and panties... if you win I'll clean our new apartment up at college for six months... deal?"

Caroline thought about his proposal and was anxious to agree, after all she was the brains in the family and Mark was the jock... although he did have pretty good grades too..."Alright it's a bet but if I win you'll not only be cleaning our apartment for six months but you'll do it in nothing but your underwear... and I can invite people over to watch you... deal?"

"Deal!" They sealed their wager with a toast of their sodas.

Nine months later, on the second of June, their respective report cards arrived in the mail and the contest was over, well almost over, Caroline still had to pay off the bet.

After they had compared grades she looked at the brother. "Look Mark," she cooed in her sexiest voice, "you aren't really going to make me do this are you; I mean its sick for Christ's sake, and besides you're my brother!"

Mark just smiled at his sibling. "Sorry sis it may be sick but I've worked the whole year just for this moment, now it's time for you to pay up!"

That Saturday night their parents left for a bridge game at the Henderson's and Caroline and Matt were finally all alone. They watched as their parents drove off then Matt turned to his sister and leered. "Well sis, are you ready?"

Caroline sadly shook her head knowing that pay up time was here and there was no way out. "Alright, let's get this over with."

Mark smiled and headed up the stairs. "I'm going to take a shower; I'll meet you in mom and dads room."

Caroline crooked her head. "Mom's bedroom... why there?"

"You'll find out." Mark went into his bedroom and stripped out of his clothes then went into the bathroom and stepped into the shower. Mark was a decent athlete playing second-string linebacker on the football team and third base during spring baseball. He stood 6' 2" and weighed just over 175 pounds and was considered a 'good guy' by most of the high school girls... still, although no one knew it, he was a virgin. Mark had consciously abstained from sex while in high school, mostly because he was concerned about catching an STD but he was even more concerned about getting a girl pregnant. He adjusted the water and lathered up his body paying special attention to his cock. He knew that if his sister jack him off right now he would cum too quickly and that was the last thing he wanted, he wanted his session with Caroline to last for a long time. That morning he had masturbated using an image of his sister jacking him off to cum and now he leaned against the shower wall and jacked off again this time thinking about his mother and pretending that she was blowing him. He had often used his mother as a sexual fantasy mostly because she looked so much like his sister and today her image worked just like it always did as his cock spurted rope after rope of cum on the shower floor.

There was a voice from out in the hallway. "Hey... what's taking you so long, you're not jacking off are you? You better not be!" Caroline yelled through the closed door.

"I'll be right there sis." He turned off the water and grabbed his towel and dried off then donned a terry cloth robe and walked across the hall and into their parents' bedroom. Caroline was already in the room, standing by the end of the bed in a pair of shorts and a blouse.

Caroline watched as her brother entered the bedroom and she could see the small bulge in the front of the bathrobe. Although she had dated since her sophomore year she had never gone any farther than light petting, letting one boy touch her breasts and suck on her nipples and then in her senior year Jim Hauser had managed to slip his hand underneath her dress and inside her panties where he rubbed her clit until she came. After her climax she lay back against the backdoor of the car panting, her breathing labored and watched as Jim started taking off his pants. When his pants hit the car floor she panicked knowing he expected the same treatment he had just given her. Caroline grabbed the door handle and flung it open and raced into the house and that was a close to having sex as she had come.

Mark looked at his sister and her far away gaze. "What are you thinking about sis?"

"Huh... oh nothing... why?"

"You look like your mind is miles away."

"No I'm right here and ready to pay off, now why are we in mom and dad's bedroom?"

"You'll see." Mark walked over to his mom's closet and opened the door and went inside and rummaged through her dirty laundry hamper until he found what he was looking for, a pair of her dirty panties. He grabbed them and balled them into his fist so that they weren't visible then he walked back over to the bed, stripped off his robe and, his cock already getting hard as his sister watched him, he hopped up onto the bed and waited for her to get undressed too.

Caroline sighed and then walked over to the side of the bed and sat down next to her brother and looked down at his cock. It was a lot bigger than she had thought it would be, maybe six inches or so and really thick. She started to reach for him but he stopped her, grabbing her by the wrist.

"Oh no you don't! You agreed to do this in your bra and panties so strip sis."

Caroline took a deep breath then shrugged her shoulder and began to unbutton her blouse. She was a pretty girl, not beautiful but she had never lacked for male attention. Her breasts weren't as big as her mother's but she did have a respectable 34B bust line. Her blouse off she unbuttoned her shorts and as she started to slide them over her butt she remembered that she was wearing a pair of bright red French cut thongs and wished that she had worn something more sensible like a pair of plain white cotton granny panties. Oh well she thought as she pushed her shorts down and stepped out of them and then crawled up onto the bed next to her brother.

Mark looked at her appreciatively. "Geeze sis you've got a great butt!"

Caroline looked down at her smiling sibling and smiled back. "Well thanks, I appreciate the compliment and you've got a nice looking cock. I guess that's why Mary Ann likes to get you alone in her bedroom."

Mark looked up confused. "Mary Ann? Mary Ann Barnes told you that we had sex?"

"Yup, one day after gym class she confessed everything."

"Well I don't want to burst your bubble sis but I've never had sex with anyone and especially not with Mary Ann... Christ she's a total slut. You think I want to dip my dick into that and catch God knows what?"