AITA for confronting my husband after I found out he was cheating on me with his sister?

I (34F) have been married to David (36M) for seven years. We’ve had our fair share of ups and downs, but for the most part, our relationship was solid. We met in college, fell in love, and were married a few years later. We didn’t rush things, but when we eventually tied the knot, I felt like everything was falling into place. We shared a home, built a family, and even had two kids, Olivia (5F) and Lucas (3M). I thought I had everything I wanted—love, security, and stability.

David comes from a very close-knit family. His parents, his two brothers, and his sister, Mia (30F), are all very close, and I’ve always gotten along with them. Mia has always been the free spirit in the family—outgoing, independent, and fun. She’s a few years younger than David, and they’ve always had a strong bond, but I never thought anything of it. I trusted them both.

The trouble started about six months ago, when David’s work required him to travel more frequently. He began leaving for business trips every other week, and while I missed him, I was fine with it. I knew his career was important, and he was doing it for our family. But during his absences, I noticed something strange: Mia started visiting us more often. At first, it seemed normal—she was helping out with the kids when I had too much on my plate. But soon, her visits started becoming more frequent. She’d show up unannounced and stay late, even after David had left.

I didn’t think much of it at first, but as time went on, I started feeling uncomfortable. The dynamic between Mia and David, even when he was around, began to feel odd. She started texting him more frequently, calling him at odd hours, and whenever I asked David about it, he would brush it off, saying it was nothing. “It’s just Mia being Mia,” he’d say. “She’s just checking in.” I dismissed my suspicions because I trusted David, but deep down, I couldn’t shake the feeling that something was wrong.

Then, one evening, everything came crashing down. I had stayed late at work, and when I got home, I noticed Mia’s car parked in our driveway. I figured she was just visiting, but when I walked inside, I found them in the living room—sitting too close together on the couch, laughing, and sharing a bottle of wine. My stomach dropped when I saw the look on their faces—it was one of those awkward, guilty expressions that anyone who’s been caught in a lie can recognize.

David quickly stood up and tried to act normal, but I could see the panic in his eyes. “Oh, hey, you’re home early,” he said, a little too quickly. Mia stood up too, but she didn’t say anything. She just looked at the ground. My heart was racing, and I could feel the blood rushing to my face. I asked them what was going on, and that’s when David tried to lie—saying they were just catching up. But I could tell it wasn’t the whole truth.

I demanded that David tell me the truth, and after a tense silence, he finally admitted it: he had been having an affair with Mia. I was speechless. The words felt like a punch to the gut. David tried to justify it, saying that it started as an emotional connection, and they had grown closer over time. He said it wasn’t planned, but that Mia had become a source of comfort to him when I was busy with work and the kids. And that one night, while I was at a late meeting, things went too far. They had been sleeping together for the past two months.

I was in utter disbelief. I couldn’t comprehend it. My husband, the man I trusted with everything, had been cheating on me with my sister-in-law. The woman who I had welcomed into my home, the woman I had trusted like family, had crossed every line possible.

I turned to Mia, expecting her to apologize or at least show some remorse, but she didn’t. Instead, she stood there, looking at me with indifference. She didn’t apologize, didn’t try to explain herself. She just said, “I’m sorry, but I can’t undo what’s happened.” It felt like a slap in the face. Mia had known what she was doing, and yet, she didn’t seem to care.

I couldn’t stay in that house another second. I grabbed my kids and went to stay at my parents’ house for a few days. I was so hurt, I couldn’t even look at David. He kept calling, begging me to come back and promising that he would end things with Mia. He said it was a mistake, and he had no idea how it had gone this far, but I couldn’t forgive him. This was a betrayal on a level I couldn’t understand, and it shattered everything I had believed in.

When I returned to the house, David and Mia were both waiting for me. Mia didn’t even try to apologize—she just stood there, waiting for me to make the first move. David, on the other hand, begged me to forgive him, to try and rebuild our marriage. He said he was willing to do anything to make things right, that he would go to therapy and cut off all contact with Mia. But in my heart, I knew that the trust had been broken beyond repair. I couldn’t imagine a future with someone who had been so deceitful.

After days of crying and talking to family and friends, I made the hardest decision of my life: I asked David for a divorce. I didn’t feel like I could ever trust him again, and I couldn’t live in a marriage where he had betrayed me so deeply. As for Mia, I told her that I couldn’t have her in my life anymore. I cut off all communication with her and told her she would no longer be part of my family.

David is devastated, and my family is divided. Some think I did the right thing by walking away from the marriage, while others say I should have tried to work things out for the sake of the kids. As for Mia, she’s still with David, but I haven’t spoken to either of them in months.

Now, I’m wondering if I made the right choice. Some say I’m justified for ending my marriage over an affair, but others think I overreacted. I feel like I’ll never trust again, and I wonder if there’s any chance of healing after something so damaging.

So, AITA for confronting my husband after I found out he was cheating on me with his sister?