Taboo fantasy come true

It's late and your older stepsister just had a fight with her boyfriend over a new proposed roleplay. She vents her frustrations while also trying to dodge your question on what it was exactly the fight was over. Finally, she admits to having taboo fantasies and her boyfriend found it just too weird after seeing how close the two of you are. She randomly asks you how your relationship is going and mentions how she even resembles your girlfriend a little. You're shocked at the question that comes out of her mouth next. Do you think of fucking your stepsister? Suddenly you find it difficult to hide your erection and the next thing you know you're inside of her. How did it come to this? You both know it's a taboo fantasy for a reason--you're not supposed to act on it!! And yet, her pussy is so irresistible. Her dirty talk too much. The arousal and desire to breed with your stepsister building up to more than you can handle. She begs you to just fill her pussy up and impregnate her with your creampie...and so, you do.