Pushing her to fuck her own

*This fantasy is via the husband's POV* Stepmom thinks she's been hiding it well, cheating on her husband. He's had his suspicions & they proved right. How could she?! They even have a young stepson together! He doesn't want this clan torn apart though. He'll give her an ultimatum. If she fulfills his dark desires, she'll be forgiven. It's only fair. It's a fantasy he's had for a while. So absolutely taboo but so hot. He wants his sexy wife to fuck their coming of age step stepson. He will watch while his wife takes REAL GOOD CARE of their boy until he shoots his seed into her fertile body. She'll HAVE to do it. He'll relish in the vengeful pleasure of seeing his wife wincing & pleading for mercy. Cheating bitch. She wants to fuck around? FINE. Now she can fuck around with their own stepson...