A friend told me she signed up at Ashley Madison, the site for cheaters, and that she was meeting all kinds of interesting (married) men on it, so I went and checked it out, more out of curiosity than any real desire to sign up. Lo and behold, I found my brother on it! He's married to a wonderful woman, has two gorgeous kids, and seems happy with her. He and I aren't joined at the hip like some siblings but we’re close enough that I would expect to know if he was having marital troubles. Since I've found him, I can't stop checking his profile; he's active on the site daily and worst of all, he's a little strapped for money right now, so it kills me to know he's spending money just to chat with women (that's how the site works, the guys have to pay to play). I know you're going to tell me to approach him privately and ask about it but I honestly don't know if I can do that. I have no idea what to do but I can't sit aside and do nothing either.

He Said: You have a classic case of conflicting rights here. The first, and triumphant, is the right of your brother to privacy about his intimate life. While stumbling across his profile was not intentional, it was still a violation of his reasonable expectation that he could peruse the site without the knowledge of a family member. Therefore, you must not only keep the knowledge to yourself, you must proceed as if you have no knowledge of the situation, especially since your own moral standing is compromised by your prurient interest in his sexual and romantic life. Not only should you not cast the first stone, you must pretend that you do not even have a stone in your arsenal. 

You must also consider the rights of your brother’s wife. Hopefully, he is transparent with her about his extramarital activity because she requires that information to make good decisions about her own intimate life. However, in this case, your brother's right to privacy trumps her right to know, assuming they do not have some kind of agreement about the openness of the relationship. So unless she brings the topic up, in which case you would need to tell the truth, keep the information, wrongfully acquired, to yourself. 

She Said: That was an elegant thesis on everyone’s boundaries, which I kind of agree with, but as usual I’m going to play this one from my gut. You inadvertently stumbled on this information, and you say you are close to your brother. If it was me, I’d simply say, next time I got him alone, “I ran into a profile of you when I was browsing on Ashley Madison. I don’t want to pry, and you know I love you unconditionally, but if you want to talk about anything, I’m here.” That’s all. Just repeat those words until you know them by heart, and say them next time you see him. If you absolutely can’t say them, then email it to him. This is 2013 in San Francisco, and your brother’s marriage and the way he and his wife conduct it isn’t yours to fix. You actually have no idea what kind of spoken or unspoken agreements they may have, and you also have no idea what his wife might be doing in her spare time—if your own brother can hide such a secret, surely your sister-in-law can too. Cheating is common and as old as monogamy. Marriages have been surviving it for ages. Your job is to offer any support you can and then stay out of it. Only if your brother breaks down sobbing, confesses to being a sex addict and begs you to help him stop should you go any further than a casual, I’m-here-for-you statement. And I’m sure I don’t have to say this, but stop looking up his profile.