You can't choose your family but you can build your own tribe.
Stepgranny knows all your secrets and she just happens to know about the taboo sex you've been having with stepmommy. She knows you've always craved having a stepaunt that youve dreamt of the companionship and love with. So she offers up her ancient artifact as a kindred spirit of your stepaunty, cut from finer cloth, she's saved room for your seed and is sure she's still impregnable!
Stepmommy is furious when she hears you 'cheated' with a different forbidden hole! She's not ok with it and demands you to do the same to her! You're called a very greedy boy! You've been longing for that companionship, that family tie and special bond with more than one familiar hole and now your back deep in your stepmommy who's got everything you need.
Your wild seed must never be let outside boy!