AITA for confronting my husband after discovering he was secretly involved with my sister-in-law?

I (34F) have been married to my husband, Ethan (37M), for nine years. We met at university, connected instantly, and got married two years later. We have two children—Sophie (7) and Jack (5). Our life seemed stable, happy, and ordinary. Ethan appeared loving, attentive, and trustworthy.

His younger sister, Rachel (30F), has always been part of our family life. I considered her like a friend, almost like a sister myself. She helped with family gatherings, holidays, and even babysitting occasionally. I trusted both Ethan and Rachel completely.

About a year ago, subtle changes began to appear. Ethan started taking longer “business trips,” spending late nights at the office, and became secretive with his phone. Rachel also began visiting our home more often, sometimes alone, sometimes with Ethan. Small details, like Ethan leaving the room whenever Rachel called or checking messages secretly, started raising red flags.

One evening, I returned home unexpectedly from work and found Ethan and Rachel in the living room, sitting unusually close, whispering, and laughing in a way that didn’t seem innocent. My stomach sank. Something about their interaction seemed intimate and secretive.

Over the next few weeks, I discreetly gathered evidence. I discovered messages and emails between Ethan and Rachel, filled with flirtation, intimate jokes, and hidden plans to meet privately. They had been carrying on a secret emotional and physical connection behind my back. My husband and his sister—the two people I trusted completely—had been deceiving me for months.

I confronted Ethan. At first, he denied everything, claiming I was “reading too much into things.” But when I showed him the messages, he admitted to the affair. He said it started emotionally but “escalated” over time.

I also confronted Rachel. She admitted she knew he was married but claimed she didn’t mean for it to escalate. The combination of deceit from both my husband and his sister left me feeling humiliated, heartbroken, and utterly betrayed.

The emotional toll was overwhelming. I couldn’t sleep, eat, or focus. Every memory of Ethan—the trips, birthdays, quiet nights at home—felt tainted. I realized I could no longer trust him, and I couldn’t stay in a marriage with someone who had deceived me so thoroughly.

After weeks of reflection, speaking with close friends and family, I asked Ethan to leave and filed for divorce. Some friends told me I should forgive him for the sake of the children; others said I did the right thing—betrayal of this level cannot be forgiven.

Now, months later, I am slowly rebuilding my life with Sophie and Jack, focusing on healing, work, and my children’s emotional well-being.

So, AITA for confronting my husband after discovering he was secretly involved with my sister-in-law?