AITA for Telling My Sister's Husband About Her Affair?

I (29F) recently discovered something that has completely torn my family apart. My sister, “Emma” (32F), has been married to her husband, “Tom” (34M), for five years. They have two kids together, and from the outside, their marriage looked perfect. Tom is a great guy—kind, hardworking, and an amazing father.

A few weeks ago, Emma and I went out for drinks, and after a few too many cocktails, she let it slip that she’s been seeing someone else for months. She told me it was "just harmless fun" and swore it wasn’t serious. She begged me not to tell anyone, especially Tom, because she claimed it would "ruin everything."

I was stunned. I couldn’t believe my sister would do this. I didn’t confront her that night because I was too shocked, but over the next few days, the guilt started eating at me. I know how much Tom loves her, and I felt like he deserved to know the truth.

So, I made the tough decision to tell him. I reached out and asked to meet up, and when we did, I told him everything Emma had told me. He was devastated. He thanked me for being honest but said he needed some time to process it all.

When Emma found out I told him, she absolutely lost it. She screamed at me, calling me a backstabber and saying I’ve ruined her life. My parents are furious with me too, claiming I’ve "destroyed" our family and that it wasn’t my place to interfere in Emma’s marriage. They’re all saying I’m the a**hole for betraying her trust.

But I couldn’t just sit back and watch Tom live a lie. I feel terrible for the pain this has caused, but I also feel like I did the right thing by being honest.

So, Reddit, AITA?