LI (19M) attended my dad’s wedding last weekend. He married Kevin (36M), the guy he cheated on our mom with. I was 16 when it came out that our dad (44M) had been having an affair with Kevin for months. Our mom was blindsided.

It was messy and ugly and destroyed our family. My little brother, “Sam” (14M), took it especially hard. He hasn’t spoken to our dad unless absolutely necessary, and definitely never accepted Kevin. I’ve been more neutral, mostly for survival cause I still need help with school, rent, etc.

Anyway, our dad basically pressured us into being part of the wedding. Sam didn’t want to go at all, but our grandparents begged him, so he caved. I should’ve known something was up when he got real quiet the morning of.

So here’s what happened:

Right before the ceremony, while everyone was getting ready, Sam offered to help Kevin with his tux jacket. Kevin handed it off while checking his phone or something. Sam slipped away for a few minutes, then came back all innocent.

What none of us knew was that Sam had taken a little container of itching powder he ordered online, and rubbed it into the armpits and collar lining of Kevin’s tux.

Cut to the ceremony: Kevin starts fidgeting. Then scratching. At first it was subtle, but by the time they got to the vows, he looked like he had fleas. He was tugging at his neck, rubbing his underarms, visibly sweating and red. Guests started whispering. Our aunt asked if he was having an allergic reaction. My dad looked confused, Kevin looked miserable, and Sam was sitting there with the blankest expression I’ve ever seen.

Kevin ended up rushing out before the ceremony finished. They had to stop everything for 15 minutes while he changed into a backup suit. The photographer had to scrap a bunch of photos. And of course, people started asking questions.

Afterward, my dad pulled me aside and asked if I knew what happened. I said no, because technically I didn’t (but I had a pretty good idea). Sam confessed to me later and said, “He didn’t cry, but he’ll remember it. That’s enough.”

Now our dad isn’t speaking to either of us. Kevin’s family is saying we sabotaged their most important day, and my grandparents are saying we both need to apologize. I don’t think I will.

I didn’t plan it, I didn’t do it, but I also didn’t stop him.

So… AITA for just letting it happen?