This is NOT a slow burn - we get straight to the good stuff in this one!
You have a StepSon to StepFather chat and he confides in you that he and your StepMom's sex life has took abit of a downward spiral, he has always fantasized about seeing her get fucked by another Man but none of his mates are down for it. Being the good StepSon that you are - you offer to fuck your Step-Mom so that he can live out his cuckold fantasy. To your surprise, both of your StepParents are grateful for your help.
However when StepMommy sees how much bigger you are, how much better you are at fucking her than your StepDad, the only person she wants to fuck is you now. You ignore your cuck StepDad sat in his little cuck chair in the corner while your StepMommy begs for your cum... erm this wasn't part of the plan... she isn't on any contraception. The cherry ontop of this filth sundae would be to get your StepMother pregnant. Your pathetic, small dicked cuck StepDad can look at his Wife's pregnant belly knowing that it's his StepSon's...