I went through the other side of this when I was 18. I simply stayed away from him after that because I got tired of hearing “I can’t believe you fucked my stepmom” constantly. No one would have ever known had he not told them and he told everyone. He was a laughing stock because he wouldn’t keep his mouth shut. Her intent was the same as mine, to have a little enjoyment. Your stepson needs to figure out that he does not own you. You are an independent woman with needs and desires. You are reaching your sexual peek and so is your stepsons friend. It’s a great match so long as you both realize that it is only physical and not love. And for the love of God, use protection so you don’t get pregnant and have to start raising all over again. Can you imagine being 60 and still having a in the house? You would never build enough savings to be able to retire! You have done your part, you raised a good, responsible stepson. He is not just concerned about his reputation but you to.