They are discovered by their mother, Monica.

• Sarah and Adam were naked on his bed.
• Sarah was riding her brother's cock cowgirl style.
• Adam was groping his sisters tits.
• Both were panting and moaning heavily.
• Although the room reeked of sweat and sex, the very pleasant, arousing and intoxicating scent of Adam's cum overshadowed most of it.

That was the picture presented to their mother Monica, and the position the siblings were discovered in, leading to their mother letting out a high pitch shriek of dread and distress.

Monica couldn't believe her eyes. She never had imagined the possibility of catching her children in an sexual act. An act that was declared taboo by society. She couldn't explain or understand how it could possibly have come to his, she had never seen any hints or signs of attraction or of an incestuous relation between her children.

"Adam? Sarah? You can't ... Why..? Stop..."

Adam looked up at his mother with was a fierce determination in his eyes. He should probably be embarrassed or ashamed, but he wasn't. The "Growth X" overdose hat taken away almost all of his morals, and had replaced them with a powerful will of seeking pleasure and sexual dominance. He had easily made his sister Sarah his first slut, and in that moment he knew that his mother would soon follow and become his second. He knew that there simply was no way to resist his huge cock.

He grabbed Sarah around the waist, and to her disapproval, he slowly lifted her up from his shaft. Monica couldn't believe her eyes: Her son's dick, which had been completely inside the pussy of her little girl, slowly came into view. It was so very thick and slick with their combined juices. She had never seen a cock that thick, and it caused a strange arousal inside her. She knew that she shouldn't become aroused by her children, that was so wrong, but she couldn't help but gasp, as one inch after another of her sons's huge cock appeared. Goosebumps formed on her skin, her face became flushed and her own nipples became hard. She could already see several inches of the long shaft, and it just wouldn't end. Adam continued to lift up Sarah, and when he was done and put her down on the bed, Monica could see that the pussy of her daughter was a gaping hole. And when she saw the full extend of Adam's monstrous cock in all his glory, she couldn't believe that it had been fully inside her daughter's pussy just moments ago.

Then Monica heard the very stern and commanding voice of her son: "I want you to come over here! Now, mother!"

And indeed Monica was unable to resist...