Part 1

Shannon sighed. It had been a long day and she was exhausted. She just spent all day with Katie and Jason at the beach. She was so glad her sister decided to send them down to visit for a week. She rarely had company and it was nice to have someone to do things with. She was afraid they wouldn't be happy to do anything with their aunt since they were both eighteen, and she knew how teenagers could be.

Katie and Jason were welcome guests in her home. At first she was worried because she only had one bedroom to put them in, but they didn't mind sharing. They were brother and sister. She should have known it wouldn't be a problem for them to sleep in the same bed.

She heard a noise and sat still to listen. It must be them, talking about what they did that day. They were still young and full of energy. They were also probably still excited. She was almost thirty and didn't have the energy to keep up with them. She didn't know how here sister did it. It must take everything she had to raise a pair of kids who were becoming adults.

They were such good looking kids, too. They both had their mother's looks. Jason was so handsome. If she were fifteen years younger, she would go after him and never let him get away. And Katie was so beautiful. It was not hard to see how she could attract a man.

She heard another noise. They seemed to be moving around their room. It was pretty late and she had to get up in the morning. Shannon decided she should go and check on them, maybe ask them to be quiet. She slipped out of her bed, put on her robe, and opened her door.

Their room was just across the hall. The door was open a crack. She could only see the corner of the bed, but she could hear them talking, although she couldn't exactly make out the words. The only light in the room was from the small night light by the bed. From inside came a familiar smell that for some reason turned her on like a switch. She pushed the door open another couple of inches and was shocked.

Katie and Jason were naked, and the dim light made their tanned skin glow. Katie, her beautiful, innocent, blonde haired niece, was on her hands and knees, her golden hair falling around her shoulders. Her brother was behind her, pushing two of his fingers into her back hole. Shannon noticed a blue tube in his other hand, and was shocked again to realize it was a lubricant. Jason was going to fuck his sister in the tail. That smell was the scent of raw sex. No wonder her body had been turned on so quickly. She grinned, despite her shock.

"Ooooh, Jason," Katie cooed softly. "That tickles."

"Does it tickle like this?" he said.

"Yes," Katie giggled.

Jason was breathing hard. Katie was rubbing her nipples and pushing her butt back on her brother's fingers. Shannon had no doubt they'd done this before. It was a mistake, she now knew, to let them share a bed together. But how could she have known they were incestuous? Dear God, she thought. Anne must not know about this.

Shannon was about to push the door open to stop them before they went too far, when she saw something that froze her in her tracks. Her nephew stood up beside the bed. He was completely naked. Shannon's mouth fell open. His cock was enormous. It hung more than halfway to his knee and looked as thick around as her wrist.

She looked at her niece again. Katie had a hand over her pussy, rubbing with her fingers and moaning into the mattress. She was already coming. Jason was going to put that thick thing up his poor sister's ass. How could she stand to accept something so big in such a small opening?

Shannon was frozen to her spot. Even though she knew it was wrong, she had to see them do it; she had to know. It couldn't be possible for a petite girl like Katie to handle a cock as big as Jason's. She wished it was her in there on that bed with her ass in the air. She would like to find out if she could handle it herself. Her hand went down to her crotch. She was wet. How long had it been since she was fucked in the tail? Not since college, she was sure.

Jason squeezed a glob from the tube of grease and smeared it all over his cock. In the light, it looked like it was carved from polished marble. Shannon's mouth watered as she stared at it. She longed to feel it in her hands and moving between her legs. Jason put some more grease on his fingers and rubbed it into Katie's hole.

"You ready?" he said.

"I'm ready," Katie sighed. Her ass moved back and forth in a slow gyration like she was already getting fucked.

Jason got on the bed on his knees and moved behind her. Shannon had a perfect view. Katie reached back with both hands and pulled her cheeks apart. Her shiny hole looked anxious to receive him. Jason raised his cock and touched the head to it. Katie gasped.

Shannon gasped and squeezed her hand over her mouth, hoping they hadn't heard. They didn't stop. Apparently they didn't.

"Ooooh, Jason... Easy... Easy," Katie moaned.

Jason pressed the head of his cock against her opening. It disappeared inside her and Katie groaned. Her voice was muffled by the pillow. Shannon winced in sympathy. She could imagine how much it must hurt to have that thing stretch her open, but she couldn't imagine how good it felt once it was inside. As Katie pushed herself back to meet him and the length of his cock plunged into her body, Shannon wished it was her on that bed on her hands and knees. She wanted Jason's cock pushing deep into her tail, too.

"Jesus, Katie," Jason moaned. He put his hands on her hips and started to move back and forth. "You're so tight. You were never this tight before."

Shannon's head spun. How long have they been doing this? she wondered. Such possibilities were difficult for her to conceive.

Katie was rubbing her pussy and moaning into the pillows. Shannon knew her ass was squeezing around Jason's cock. She knew how it felt. She remembered the last time she got fucked in the tail and how tight her asshole got when she was cumming. It was an incredible sensation. Her niece was feeling it at that moment.

Eventually, she gave up on rubbing her pussy and clutched the sheets by her head. Jason was pounding his cock into her ass. Katie was having a beautiful orgasm, and Jason pumped her right through it. Then his body became rigid and the muscles of his body tensed. Shannon knew he was shooting his cum into her, filling Katie's small body with it.

Shannon felt waves of pleasure pour through her own body. She had to hold the edge of the door to keep from falling over. Katie lay flat on the bed and Jason lay on top of her with his cock still wedged into her ass. They were kissing and fondling each other. Shannon didn't stay to watch. Quietly, she stepped back across the hall, closed her door, and jumped back into bed with her fingers jammed in her pussy. She buried her face in her own pillow and moaned through her own orgasm.

Katie and Jason had glowing faces in the morning. They gave each other quick glances and smiles. Shannon pretended not to notice, although the secret was killing her. She was dying to ask Katie how it felt, to ask Jason to show her his penis. To look at them, she thought, it was difficult to believe she actually saw them having sex. If the image of them naked on the bed wasn't so clear in her mind, she might have believed she imagined the whole thing.

Katie changed into her swimsuit, a skimpy bikini, and grabbed a towel. She wanted to go down to the beach to work on her tan before the sun got too hot. Shannon wanted to object to the bikini she wore; it was a thong back and barely contained her swollen breasts, but she bit her tongue. After what she saw them doing last night, she hardly felt it was appropriate for her to tell them anything.

Jason volunteered to wash her car, a 1966 Mustang convertible, and went out to the front yard with the hose and a bucket. Shannon stood at the window and watched him, unable to wipe the smirk from her face.

Jason removed his shirt and shoes to wash the car, her own baby. He looked like a young god. He had a surprisingly well developed, muscular body for a man who just turned eighteen, but it was the muscle in his shorts that interested her. She imagined laying back on her bed with her legs spread, watching him come toward her with that thing hanging between his legs. The thought of him pushing it into her and wrapping her legs around that chiseled body made her dizzy. She decided to be bold and do something about it.

In her bedroom, she changed into her own bikini and stood looking at herself in the mirror. She still looked good, she decided. Maybe a little more plump than when she was Katie's age, and maybe her breasts weren't as big as Katie's, but she still looked good. Hopefully, she looked good enough to arouse Jason.

As she went to the kitchen and made a pitcher of lemonade, she thought she was crazy for what she was about to do. Anne would kill her if she found out she was going to seduce her son. But she had to know; she had to feel it for herself.