Link to my original post: https://www.reddit.com/r/relationships/s/vaUuBhkOwI
First off thank you everyone for your advice. I think i was still kind of in a mode of shock and panic and reading your comments helped me sober up. I appreciate you all.
I’d also like to quickly address those of you who suggested burying it because “I have no ties to this woman” or “he’s your friend not her” or “bros before hoes”. This isn’t some random girl he just started hanging out with. They’ve been married for 7 years and were dating for 2 before that. She’s been a big part of our lives for nearly a decade and is my friend in her own right, even if she doesn’t share the same history me and her husband do. So the idea that I have no ties to her or owe her nothing is just wrong.
The evening after posting this I told my wife. You all were right that I shouldn't have kept it from her in the first place. She listened to what happened and then sat silent for a minute. I was afraid she was going to be mad at me for not telling her like a lot of you said, but no. She said that a part of her was relieved because she could tell that something had been severely bothering me these past couple of days, but aside from offering the occasional "are you ok?" she decided that I would tell her when I was ready to share. Though, when I told her about the thread, she was slightly annoyed and thought it was silly for me to have brought my problem to a bunch of strangers on the internet before I brought it to her. I apologized for not telling her sooner and for waiting to act despite knowing in my heart what I needed to do. My wonderful, amazing, and astoundingly understanding wife responded with, "even when we're sure what is right, it's only human to hesitate when we know it's going to cost us dearly."
That said, she and I are all good.
After our discussion, I showed her the thread. She read comments for nearly an hour before we started talking again. Ultimately we decided that we had to tell my friend's wife (who I will from here on refer to as Sister so I don't keep having to say friend's wife). The reason we did this instead of an ultimatum is my wife was concerned he would use the time to cover his tracks or orchestrate her opinion against us. Neither of us really felt that would be in character for him, but we wouldn’t have thought it in character for him to cheat either. My wife texted Sister and asked if she could come over after work the next day (Sister works mostly evenings so she usually gets off around 11.) My wife had told her it was a serious conversation so Sister was pretty tense when she arrived at our house. We sat her down and we told her everything. After hearing it, she took a long breath and said, "I've known for a couple of weeks." Apparently, she had asked her boss if she could go home early one night a few weeks ago because she wasn't feeling well, and found he wasn't home. She texted him asking what he was up to and he said he was "at home watching tv." She tried to look up his location on their tracking app but it was turned off. She left home and waited until when her shift would normally end to return. He was home when she got there and when she asked how his evening was or if he did anything interesting, he told her hed been home all evening watching tv and playing video games. She checked the app again and sure enough, his location was turned back on. Sister said that, until we told her, she didn't have any proof but felt she knew what must have been happening. We asked her what she was planning to do now that she knew.
Here's the part I didn't see coming: she plans to move forward with IVF. According to her, it's always been her lifelong dream to be a mother and without IVF it will never happen. IVF is expensive. She won't be able to afford it on her own and she's afraid that if she leaves her husband she'll never get another chance. Her current plan is to follow through with implantation and decide what will happen to her marriage afterward. She says they have a healthy embryo and she wants to give her child a chance, even if it means she could end up raising the child on her own. When I asked if threre was any way she could see them reconciling when this is all over, she said it depended on him. In the end, she asked us to please keep it quiet and not tell him that she knows. We agreed and assured her we'd be there for her if she needed anything. I called my friend the next day and told him that, while I still love him, I need space after learning what he did and that we wouldn't be seeing each other for a while.
I still feel a lot of things: relief from not bearing the secret, sorrow for sister and what I fear she's going to have to go through, anger at my friend for destroying our family as it has been (if not destroying it entirely), and grief from what feels like the loss of the person who has been with me my whole life. I hope for all 3 of their sakes they can work it out, but I know those chances are slim. This whole thing has been exhausting and, while I’m not sure exactly how to move on from it, now I can at least try.
Thank you all again for your help. I doubt I’ll have any more updates
TLDR: we told my friends wife about his affair but she still wants to have his baby.