AITA for confronting my husband after I found out he was cheating with my best friend’s sister?

I (34F) have been married to my husband, Kevin (37M), for nine years. We met at university, bonded instantly over shared hobbies like photography and travel, and got married three years later. We have two children—Ella (7) and Sam (5). On the surface, everything seemed perfect. Kevin was attentive, charming, and always made me feel loved.

My best friend, Julia (33F), has been in my life for over a decade. We share everything—secrets, advice, celebrations. I trusted her completely. Her younger sister, Vanessa (30F), I had met only a few times, and I assumed she was harmless.

About a year ago, I began noticing strange behavior. Kevin started staying late at work more often, leaving his phone in another room, and being unusually defensive when I asked questions. Vanessa also began visiting our house more frequently, sometimes alone, sometimes with Julia. I initially thought nothing of it—maybe they were bonding—but the feeling in my gut told me otherwise.

Then one evening, I came home early from work to surprise Kevin. I found him and Vanessa in the living room, sitting uncomfortably close, laughing in a way that didn’t feel innocent. My stomach dropped. I stood frozen, unsure if I should confront them immediately.

Over the next few weeks, I monitored signs and discovered messages on Kevin’s phone between him and Vanessa. They had been exchanging flirtatious and intimate texts for months, making plans to meet secretly. Kevin, my husband, had been betraying me with my best friend’s sister—the one person I assumed was safe and neutral in my life.

I confronted Kevin. At first, he denied everything, saying I was imagining things. But the messages, timestamps, and even photos left no room for denial. He admitted the affair had been ongoing for six months. He claimed it started emotionally, that he felt neglected at home during my busy work hours, and that Vanessa had “understood” him.

I was devastated. How could he betray me with someone connected to my best friend? It felt like a betrayal layered on betrayal. I also confronted Vanessa. She claimed she didn’t intend to hurt me, but she clearly knew he was married and involved with me. Her indifference only made my anger stronger.

The emotional toll was unbearable. I couldn’t sleep or eat. Every time I looked at Kevin, I felt disgusted and betrayed. The trust that had taken years to build was completely shattered.

After weeks of reflection and speaking with close friends, I decided I couldn’t stay. I asked Kevin to leave, filed for separation, and cut off all contact with Vanessa. Some friends think I overreacted, saying I should forgive him for the sake of the children. Others support me, saying betrayal like this is unforgivable.

Now, months later, I’m rebuilding my life, focusing on my children and career, learning to trust myself again, and understanding that protecting my emotional well-being had to come first.

So, AITA for confronting my husband after I found out he was cheating with my best friend’s sister?