Anal

Then David felt his son taking aim with the head of his cock, and not at his pussy as he had expected. Jacob pressed his cock against his little sister's asshole, slowly increasing the pressure.

"Jacob, what are you...."

Before he could finish, Rachel's asshole began to stretch and Jacob pressed in. David was surprised at the ease with which his youngest daughter's ass stretched out. There was very little of the pain he had been expecting.

"I know you only do anal because you want to stay a virgin til marriage," his son was saying. David was suddenly horrified by the idea that his little girl was into butt sex, but he hardly had time to process the thought before Jacob started fucking him.

"Oh god," David moaned. He looked up into the bathroom mirror and saw the image of his son ass fucking his barely legal daughter. He was so ashamed and disgusted by himself...yet he was more turned on than he had ever been. Without thinking he moaned, "Harder!"

"God, you feel so good," Jacob said, taking a firm grip on his father/sister's hips so he could go harder.

"I'm...gonna....cum...."

At once David felt the muscles in his pussy begin to contract as an orgasm washed over him. He was barely even aware of the sound of the controller as it began to beep.

In the mirror, suddenly Rachel faded into his own reflection, and his daughter's experienced asshole became his own, which had been completely virgin until a split second before. Each thrust of Jacob's cock felt like it was ripping him in half.

"Oh fuck thats...so...tight...."

Then he felt a sudden warm feeling as his son emptied his balls deep inside his ass. To make things even worse, David began to cum as the sudden and unexpected action hit his prostrate just right.

"Dad?" Jacob suddenly cried, jumping backwards. His cock slipped from David's ass with an audible sound. "What the fuck?!!!!"

"That wasn't supposed to happen," David moaned.

"I just ass fucked my own dad," Jacob said in shock. He turned and once again ran out of the room.

David could only stand there feeling sore as a mixture of his son's cum and his own ran down his thighs. This device wasn't working out the way he had planned....