TL,DR: My boss is about to marry and spend a lot of money on a much younger co-worker who is cheating on him. Do I share what I know?

My boss, Wesley, recently told me that he plans to marry Gina and take her to Europe in about 6 months or so. I know that Gina has been cheating on Wesley. A few other coworkers know as well. I told my husband, who works with us. Another coworker accidentally saw snapchat messages between Gina and the guy she's sleeping with, Nic, on Nic's phone screen while at work. Yep, the other guy is also an employee. It's definitely messy, but it's a very small business, only about 20 employees. There's just no HR to report to or to enforce policies about these things.

Wesley is about 35-45, divorced, uncertain number of children he doesn't talk much about. What he does talk about is his ability to hook-up with women. He works, hooks up, and follows sports. That's about all I know about him. He has little respect for women. But he's my boss, not a prospective partner. His personal life has nothing to do with me. Until it did.

I had become friends with Gina when she started. She was young, having started shortly after graduating high school. But she was a good worker and I enjoyed her company as a coworker. She brought her boyfriend to work and introduced him. He was wonderful and she seemed reassured that I approved. They got an apartment and moved in together, which did seem a little soon. So when she voiced a lack after of interest after a little less than a year, I cautioned her to give it thought. I didn't know then that she had started sleeping with our boss. It began right about the time that she turned 20.

When the relationship between Wesley and Gina was out and common knowledge at work, Gina asked me and my husband if we thought she was crazy. We considered her a friend, and were concerned given the significant age gap and power dynamic. We cautioned her and pointed out Wesley's reputation with women, which was also very common knowledge at work. When we arrived at work the following day, Wesley greeted us with a finger in the face and a stern warning to stay out of his personal business.

Gina was promoted to a position of mild/moderate authority over other coworkers. She began aggressively harassing other coworkers. Any complaints were met with an explanation that she was struggling with her mental health and to just avoid her. Nothing was effectively done to assist or protect the coworkers that were being harassed, and we began loosing employees.

Gina became pregnant and had a baby shortly after turning 21. Wesley got her an expensive engagement ring. Gina's demeanor changed and she became much more pleasant to work with. The relationship seemed genuine and I was willing to support it, from a distance, as a coworker. But I was never going to trust Gina enough to be friends again.

A while back Gina said that she had given notice. I knew that she wanted to leave the job. I knew it was what Wesley wanted. He'd commented before that he makes enough that Gina doesn't need to work at all. I asked Gina what she'd be doing, and I was surprised when she told me that she was moving out of state to be closer to family.

Shortly after that exchange, I got a phone call one night from a former coworker that Gina had briefly dated. I'd stayed in touch with the guy after he'd left, about two years prior. It wasn't too strange for him to call me. But it was very strange that Gina had just called him after not reaching out to him in well over a year. Apparently Gina was having car trouble nearby and didn't know who else to call, but this guy couldn't leave his young sleeping child to help, and he was suspicious. I went to see what was going on myself. I pulled into an empty parking lot and saw Gina with Nic. They admitted that they were hooking up. I helped them get on their way and promised not to tell. What would it matter if Gina is days away from moving? She was talking as if that would effectively end her relationship with Wesley. And Nic just up and quit right about the time Gina left, so it all seemed irrelevant and not any of my business.

Recently, Wesley mentioned that Gina was coming back to town. Apparently she was just visiting family? And he's planning to marry her and take on a trip to Europe sometime in the next six months. I honestly hate the deception and selfishness of cheating. But I also can not identify any moral obligation to disclose what I know to Wesley. There's always a good chance that he won't believe me. Although I have plans to leave this job, I can't just yet. There's also a petty part of me that keeps thinking about that warning to stay out of Wesley's personal business. Perhaps this is karma. My husband is furious. He doesn't think that any man deserves to be used like this. But he understands and agrees with my reasons for not speaking up. And who knows, maybe it will unravel on its own before Wesley gets in too deep.

Am I wrong? What would others do in my position?