ISTORY
Nathan heard them as soon as he walked in the door. "Oh God... oh God... Yes... Yes, yes... yeah, baby..."
His sister Shelli and her boyfriend Mark. It figured.
Their parents were away overnight. Shelli had warned Nathan that Mark would be coming over. He'd just hoped he'd be gone by the time he got home from work. No such luck.
"Oh yeah." That was Shelli's voice, low and raspy. "Keep it up, stud, keep it up..."
Nathan groaned, dropped his backpack on the floor, and made sure the door was locked. He got himself a soda and headed upstairs.
"Oh, baby." That was Mark, husky and urgent. "I'm gonna keep it up all night for you, baby. You're so fucking hot!"
He stopped halfway to his room. Damn it, they hadn't even closed the door all the way. He was about to walk past, but his feet wouldn't move all of a sudden. He stayed in the hall and leaned over to peer into Shelli's room.
Nathan's sister Shelli was two years older than him--22. She had long blond hair and she was on the swim team, so her shoulders and legs were tanned and muscular. Her boobs didn't look that big in the swimsuit she wore at meets, but whenever Nathan saw her in a bikini, he couldn't ignore the fact that his sister had nice tits, boobs that were straining to bounce freely.
And they were bouncing now. Shelli was on her hands and knees and Mark was behind her, slamming his cock into her pussy hard and fast, and Nathan could see his sister's tits swinging back and forth with each thrust as she moaned and shook with pleasure.
"Oh yeahhh," Shelli moaned. "Yes, yesss, God yes..."
Mark clutched Shelli's ass, grinning as he fucked her. His eyes werwide as he looked down at her body, and he was biting his lip to hold off from cumming a little longer. His back was sweaty, and hairy, and he looked as if all he could think about was fucking Shelli all night.
Disgusted, Nathan started to walk away.
Then Shelli turned her face toward the door. For a moment she looked confused, as if she'd forgotten where she was and everything around her except Mark's thrusting dick inside her. Then she blinked as she saw Nathan, her brother, watching her, and she smiled. She winked at him.
Nathan stared back at her, his mouth dry. Suddenly he felt his cock stiffen inside his boxers. He was hard--harder than he'd been in months, aching for attention. He stared at his sister, naked, getting pounded by her boyfriend, moments away from cumming, and smiling at him, and all he wanted was to yank his pants down and start jerking his own dick right there in the hallway. With Shelli watching.
Then Shelli was looking away, her head down, breathing hard as her body started shaking uncontrollably. "Oh God yes," she moaned. "Oh God yes--ahh! Yes! Yeah!"
Shelli was cumming, and Mark was too, his hips jerking as his cock started pumping into her pussy. He groaned softly, holding onto Shelli's hips, his dick firmly planted inside her as he leaned back and let his cum stream inside her.
Nathan staggered back before either of them could notice him. His cock was throbbing as he made his way silently to his room, closed the door, and pulled down his pants.
***
A half an hour later he heard Mark leave, and then he heard the shower in the bathroom down the hall. He was watching videos on his iPad in bed, trying not to feel too angry at his sister.
Shelli had a right to have sex, he supposed. This was the first time he'd actually witnessed it, although he'd always known she had boyfriends and they did more than kiss and cuddle. But what bother him was Mark. He'd only met the guy a few times, but he seemed like a dumb jock, someone who thought he was above everyone else because his family had money and he'd been on the football team in high school. Shelli could have better taste in boyfriends.
But there was nothing he could do about that. He heard the shower switch off and tried to forget all about his sister.
Then she knocked on the door. "Nate? Can I come in?"
Now what? "Yeah, sure."
Shelli opened the door. She was in a long pink T-shirt, barefoot, and he couldn't tell if she had anything on underneath it. She looked in. "Whatcha watching? Porn?"
"No." He scowled. He'd been watching porn a little while ago. To jack off. Seeing her now made him think about doing it again once she left. "Lord of the Rings stuff."
"Nerd." Shelli sat down on the edge of the bed. "You okay?"
"Yeah. Why wouldn't I be?" He couldn't help looking at the bottom edge of her T-shirt and wondering if she had panties on down there.
"Sorry you saw that. I guess Mark forgot to shut the door." She giggled.
Nathan rolled his eyes. "Great guy."
"Hey, don't be mad." She patted his foot. "He's no great brain, but he's got what every girl wants."
"A hairy back and an ego the size of a Cadillac?"
Shelli laughed. "Don't be jealous, Nate."
"Jealous? I'm not--" He stopped. "Just seems like you could do better than him."
"Maybe." She tickled his leg lightly. He jerked it away. "How much did you see?"
"Enough. Too much. I should have walked away right away. Sorry." He shrugged. "Your business, not mine."