Her son, however, was finding it very hard to keep his promise. Bobby tried, but the temptation was much too powerful for him. Fearful of getting another note from school, he struggled with his feelings during school hours, but at home it was harder. His sister, two years younger, didn't seem to understand how sweet and tempting her body was to him.

Bobby wanted to feel his sister's satiny flesh, squeeze her lovable little ass, touch and rub her hot little cunt. He wanted to rub his cock on his sister's body, on her thighs, her ass, between her legs, and maybe, just maybe, see if he could put his cock into the little slit of her pussy.

Bobby tried to imagine what it would feel like to have his cock in her pussy. He knew it had to feel better than fucking his fist.

Linda moved to the patio door, watching Bobby and Sarah in the back yard. She smiled affectionately when she saw her son pushing his sister in the swing. They were not bickering for a change, and maybe Bobby would keep his word to her, she thought.

But she saw something else, too.

Bobby was pushing his sister quite high, and his cock was obviously hard. Watching closely, Linda soon saw why. Each time Sarah swung back over her brother's head, her short skirt lifted. She saw the flash of Sarah's tight panties and the backs of her slim legs. Bobby was looking up, seeing his sister, too. And each time he pushed her, Linda noticed that his hands shoved at her little ass, not the seat of the swing.

"Bobby!" Linda called, stepping onto the patio. "I want to see you for a minute."

Bobby walked to her, his eyes cast down, not looking at her. He was trying to conceal his hard-on, Linda noticed.

"You promised, Bobby," Linda said, unable to put conviction into her tone of voice.

"I didn't, Mom!" her son protested, knowing what she was talking about.

"Bobby, I was watching."

"But, Mom, it was an accident this time! I was pushing Sarah and her dress was – Mom, it was an accident!"