'Found out my BF is concealing his brother's affair. Should I end things and tell SIL?' UPDATED

"I broke up with my boyfriend because of his views on cheating"

This is a throwaway. I don't know what to feel. Me (25f) and my boyfriend (28m) have been together for 3 years now. We are have been living together for 2 years. I know his family. He has one brother, Sam (33m) who is married to Lisa (32f). They have one daughter who is 4 years old. He is very close to his brother which resulted in me being closer to his wife and kids too.

Sam sometimes comes to our place and plays video games with my bf. Oneday, when they were playing video Sam put his phone on charger in our guest room. I was there cleaning the windows when suddenly his phone buzzed. I went to look and there was a girl named "Office" texting him "I had a great time last night. Your tongue is magic." with some emojis. I was a little shocked.

Sam always shows how much he adores his wife. Even Lisa says he is the best husband. How could he cheat? This was the first incident. Then oneday when he was at our house again, he was talking loudly while I was right by the kitchen while he was talking on the phone in our guest room with doors open. He was saying "I love you" to a girl names "Beth". This confirmed my suspicion even more.

I told my boyfriend I think his brother is cheating on his wife. I asked him if he knows anything about it. His expression went blank. He told me he knew about it. I was perplexed. I asked what does he mean. He began to tell me Sam has been seeing other girls on the side. He doubled it down saying it is not a big deal because Lisa is happy, he is happy and plus he doesn't like to mix in other people's business.

I asked him if he thinks that his brother cheating on Lisa was right. How could he defend his brother over something so vile. He told me it is their personal life. Plus he doesn't want to ruin his brother's marriage. I told him firmly his brother's marriage was already ruined the moment he decided to stick his dick inside someone else that isn't his wife and he clearly wrong for supporting him.

How would he feel if I was cheating on him and my sister knew and never told him? He told of course he would feel bad. But this isn't about him. I just told him to leave me alone. Cheating is a deal breaker for me. I do not like people who are cheaters or support cheating. I can't even look at him the same way I used to. So, few weeks ago, I called him and told him this isn't working.

I cannot be with someone who supports cheating and doesn't mind someone else cheating. He cried and told me to not do it. That he will do better and this isn't fair to him. I cannot punish him for what his brother is doing. I told him calmly that this is not a punishment but my decision. I already told him that cheating is a deal breaker for me. I will not tolerate it in any shape or form. I went to stay with my brother.

Two days later I went to our place to get some stuff of mine. He asked me if he could talk. I said sure. He told me he was wrong for not saying anything against his own brother. Lisa is a good woman and that he would ask his brother to stop. I told him that doesn't make me feel better. The fact that he thinks it is okay to cheat clearly shows he has no problem with cheating on me.

He told me he's not cheating on me and that he will be better. I asked him if he could tell Lisa about his husband's affair. He went silent and told me he can't go against his own brother. Well then I guess he made his choices. I left his place leaving him crying on his couch. I feel bad. I love him but the trust I had for him is gone. I do not know how to tell everything to Lisa. I am not sure what to do. I feel lost.

Edit: To those who says that my bf is not wrong I hope you find yourself in a similar situation as Lisa. I would like to know how would you feel when you learn that your husband betrayed you and people close to you knew about it and let you get cheated on day after day. He has covered for his brother on many occasions. He has lied to to Lisa telling her that Sam is with him when he was not.

Even if he didn't him simply acting it is not a big deal that a woman who is so loyal to her husband is getting cheated on is wrong and malicious in my eyes. Him concealing his cheating is also putting her at risk of STDs and also what if Sam got one of those girls pregnant? Ever thought about that? It's not like they were in open or poly relationship.

Edit 2: I cannot comment on my own post. What is up with that? It gets removed. But to anyone who is asking, I will tell Lisa. She currently out of town. I can send her a message but I have no evidence that Sam is cheating. Plus she told me she would not be near her phone.

Do you think she did the right thing? Should she tell her SIL? This is what top commenters had to say:

Technical_Pumpkin_65 said:

You did right but tell me you tell Lisa that her pos husband cheat on her?

yggdrasillx said:

You are defined by the company you keep, and your ex picked to be on the wrong side of morality. I know it must be difficult, but love is pretty much worthless without loyalty.

[deleted] said:

I have to say your strength and determination is amazing.

Awesome_one_forever said:

He was covering for his brothers infidelity. You made the right call. If he had cheated on you, his brother would have covered for him.

Mountain_Monitor_262 said:

Congrats on recognizing a moral flaw in his character and realizing he would not make a trustworthy long-term partner. But he is afraid to expose his brother. He is relying on someone else to do that for him. Tell Lisa her husband is cheating on him and to look up office and Beth on his phone. It’s up to her what she does from there.

[deleted] said:

I would tell Lisa cuz she can catch an STD.. I had a friend who was pregnant and found out she had an std and that’s how she found out he cheated and the birth had complications.. I would just tell her and if needed call him when she is there and ask your bf again about it so she can hear him confirm it.. that’s all you can do!

Move on from him because he will do it to you since he doesn’t think it’s a “big deal” which is a mess up view.

A week after her original post, she shared this update:

Thanks for all the kind words. I wanted to make an update the day after I posted it to reassure you guys I did tell Lisa. But something came up and I was delayed. So, I did tell her the very day I made this post even though I had no evidence. I got some encouragement from you guys too. For all I knew she could scream at me.

But hey if that happens, at least I wouldn’t have to live with this giant guilt that I misled a friend of mine. I talked to Lisa telling her everything on the phone. She just told me she can’t speak right now and thanked me for informing. Which was weird. I didn’t hear from her for the next 3 days. I only heard from her when my ex called my brother to yell at me.

He called me a homewrecker because I snitched to Lisa and today she took her daughter and served Sam divorce papers. I was even more confused. It’s not possible to file a divorce paper within 3 days. I called Lisa. She didn’t pick up but texted me to come to Sam’s house. I went with my brother because I didn’t know how safe it is for me.

When I entered I saw my ex, Sam and their parents along with Lisa. Sam looked really shit. My ex jumped on me by saying I did this to his brother. Lisa told my ex to calm down. She carries on to explain that she already knew Sam was cheating for a while. One of the girls he hooked up with contacted her and showed her the messages between him and her, that girl worked in his office.

The girl felt guilty knowing that she hooked up with a married man and so she told Lisa before quitting her job. I am guessing she felt really guilty and couldn’t work there or something. Lisa further told us she has been planning on leaving Sam since then. She needed time to get her things sorted and gather evidence that will help her in court.

She was mostly a homemaker but worked part time so there were financial issues too. She went on to expose Sam even more of his deeds in front of his own parents and told Sam she wants full custody because Sam bringing one of his “wh0res” around her daughter is not safe. From what she described Sam is pretty screwed in the divorce. She also didn’t spare my ex.

She basically told him she has never treated him like an outsider. That if someone was cheating on him she would definitely tell him. Even if that someone was her own family member. She finds it really sad that she had to know from a stranger what his brother was up to rather than someone closer to her and someone she loved like a brother. My ex was silent.

A lot more things came to light because there was a lot of yelling and pointing fingers. Sam has been cheating on Lisa for 3 years. My ex knew it for the last two years and has been covering for Sam. Sam’s parents were disappointed at him as well. And apparently my ex also lied to his parents about why we broke up. He told his parents I fell in love with someone else and that’s why I left him. Why he did that?

Because his stupid brother thought it was a great cover up. Because even if I told Lisa then no one would believe in me because I was the one who "cheated" and projecting it on his brother. Lisa called me here to clean my name and also thank me for informing her even if she knew it all along. Their parents apologized to both of us and told us they are ashamed of their sons. I just felt bad for them.

After that I went home. Lisa asked me if she could stay with me. I said sure. She was stoic when she was talking to Sam and his parents but as soon as she entered my house she broke down in tears. She told me that she should have listened to her friends who told her Sam was not a decent person. She left her job and her law study so that she could be with him. I felt really bad for her.

I know this will be really tough on her and her daughter. I wish there was more I could do. But I am really impressed that she handled this situation with such poise. I hope she decides to continue her law studies like she wanted to. She sacrificed a lot for that b@stard.

Also to all those people who think that my ex was right not to snitch on his brother. You guys don’t see how he is putting her at risk? Sam was having sex with literally everything that has a hole. You guys think it would be better to keep her in the dark? I know she knew about it but what if she didn’t? What if Sam’s careless wh0ring put her in danger of STD? Some STDs are life threatening like HIV.

Him not coming clean of his brother’s deeds was seriously putting her in danger of it. And I wasn’t punishing him. I simply cannot live with someone who would support cheating. To me that is exactly like cheating. Moreover, he lied and covered for him. Who is to say he wouldn’t mind cheating on me because he clearly thinks cheating is not a big deal.

Even if he wasn’t covering for them, the mere fact that he thinks it is ok for someone to get cheated on is a huge NO for me. I am really shocked to see how many people are willing to take the cheater's side instead of the one who getting cheated on.