'Caught my BIL red-handed with his side chick. AITA for not telling his long-term GF?'

"Caught my BIL red-handed with his side chick. AITA for not telling his long-term girlfriend?"

A bit of background about me: I've known my husband for 4 years, and we've been married for 1 year. Throughout our relationship, the whole family has been aware that my brother-in-law is a well-known player. This behavior probably runs deep - it seems to come from their dad.

The situation: I'm not particularly close with my BIL. Let's call him Bob and his girlfriend Diane. Bob can be quite a jerk, and unfortunately, my whole in-law family enables this behavior, including my husband. I wouldn't say they entirely enable him; they mainly just won't interfere and hate confrontation. Unlike me, who loves a bit of confrontation and a proper conversation.

I first learned about Bob cheating on Diane when my husband (then boyfriend) and I caught him at a restaurant. The woman in his car was definitely not Diane - I had met Diane once before and knew what she looked like. At the time, I thought it was just a one-time thing and wasn't aware they'd been in such a long-term relationship. I brushed it off and let things happen.

At the next family gathering, I asked Diane how long they had been together. She answered "5 years." For context, that was four years ago. Now, they've been together for 9 years. Throughout the 4 years I've been in the family, Diane has always been here and there - I've seen her less than 10 times total.

Fast forward to last year - my husband and I got married. During our wedding, there was one woman my husband had known for 9 years. Let's call her Karen. All of a sudden, she's always in our pictures. We didn't mind because we thought she was just one of Bob's friends who had become the new bestie. But I had my suspicions.

Also last year, we only met Diane once. The family had a theory that Bob and Diane might not be together anymore. Here's where it gets juicy. One day last year, my husband went to a car shop to get his car fixed. (Cars are a big thing for my husband and his brother - it's how they bond.)

Bob was there to support him at his friend's shop. Bob got there earlier, and when my husband arrived, he saw Bob at his car touching someone's thigh. In my husband's innocent mind, he thought it was Diane because she usually goes with Bob and sometimes naps in the car after long work days.

They chatted briefly, then my husband went into the shop. Bob joined him later. While they were talking, a woman suddenly came into the shop to use the restroom. Plot twist... it wasn't Diane. It was Karen! My husband immediately texted me saying he had the best gossip ever.

This was the first of several encounters. Another time we saw them having coffee near my MIL's house. We didn't say much because we were heading to our usual cafe.

A couple months later, my husband had coffee with his mom and older brother. My MIL told them that Bob had looked flustered and anxious a few days prior. Turns out, my MIL had snooped on his phone at 5 AM and saw messages from Karen saying, "I hope you got home safely and I love you."

That afternoon, she saw messages from Diane saying, "If you don't love me and found someone prettier, you should just tell me." This message left him completely flustered. He quickly ran out the door - we're not sure what happened next.

Fast forward to this year - after a year of not seeing Diane, she surprised us by joining our family holiday trip. The last time we'd seen her, she wasn't in the best mood. Throughout the whole trip, I got to see Bob's true colors. He was an a$$hole to Diane and definitely an @$$hole to my MIL, but somehow Diane didn't seem to notice.

Maybe I'm sensitive, maybe I'm a bit feminist, but whatever - I can spot red flag behavior from a mile away because I was raised around red flag men my entire life. Somehow my MIL sees him as fragile, innocent, and naive, while Diane sees him as... God knows what she thinks of him.

Things got really interesting on our way home. My MIL suddenly told us she had a story to share. Two weeks before our holiday trip, she had run into Bob's best friend/ex-girlfriend. Let's call her Ana. During their conversation, my MIL asked about Karen and Bob. Ana got pissed when she heard both their names.

Ana told my MIL she had seen Bob staying in Karen's room all day. (Ana and Karen used to be roommates after Karen got divorced last year.) Ana got suspicious and waited for them to leave the room. When they did, Ana snuck into Karen's room and found used condoms. Ana was furious because she knows Diane exists, and Ana herself used to date Bob. How Karen could still choose to be with him is beyond.

Ana told Karen's ex-husband about this, and Karen got into a huge fight with her ex. There weren't details about their fight, but that's what Ana told my MIL.

This whole situation is on another level.

Two weeks later, my husband and I saw Bob chasing Karen through the mall. They looked like they were fighting, and I have evidence that they're definitely together.

Here's my dilemma: I want to tell Diane, but she seems like she knows but is in denial or something. I also want to protect my husband from getting into fights with his brother because I can't hold this secret anymore.

My dad was a player, and because my aunt and uncle told my mom the truth, she was able to end the marriage. It helped my mom escape from an irresponsible man. I want to help Diane the same way, but I'm stuck between loyalty to my husband and my personal values. So, AITA for keeping this information to myself?

What do you think? AITA? This is what commenters had to say:

LaMergouille said:

Like you, I believe that Diane knows but she is burying her head in the sand. Tell him or not depends only on you and your feelings, but will it be worth it to come across as the "bad guy" by saying what everyone knows/assumes. Courage to you in any case 😅

thedodoson said:

Yes you would be the a-hole if you don't tell her. And "loyalty" to your husband, that's what you're worried about? He has a sh!t brother that he enables and covers for, I'd be questioning his entire character if he condones that kind of behavior. His father is a player, his brother is one, and he's helping him cover it up. I wouldn't be questioning my loyalty to him, but his loyalty alltogether.

KatesDT said:

Nope. Back away slowly. Don’t touch this with a 10 foot pole. He is a serial cheater. Diane knows this already. You don’t need to involve yourself in any of this drama. I would tell my husband that I’m not lying for anyone. If Diane ever asks, tell her the truth.

But don’t open this door and cause stress for yourself. Some people like the drama. I would not purposely set myself up to be the bad guy for telling Diane something the entire world knows. Nope.

Sorry-Bed5144 said:

Tell her and maybe he will tell you about your husband’s affairs too.

A guy who supports a cheater is usually a cheat too :)

Stay tuned for any future updates!