Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: A few months ago, I caught my sister’s husband in bed with another girl, both naked. It was during a Christmas party at our mutual friend’s house. My sister was spending the holiday with my parents. Due to our works, my brother-in-law and I would only join them on New Year’s Eve.

I confronted him about it and he told me he had no idea what had really happened that night since he was so drunk. He also told me that the girl I had caught him in bed with had been obsessed with him since high school and ‘will do anything to win his heart’. But he has never had feelings for her let alone slept with her. He loves my sister and their son so much. He believes, based on this obsession, she had slipped something in his drinks. At least that’s what he told me. I couldn't tell if he was lying or telling the truth.

I told him that whatever might have happened that night, he still gotta tell my sister because that’s what a married couple should do. And I believed my sister will be able to tell if he’s telling the truth or not. He promised he would when the time is right.

The following weeks, I found out he had not told my sister about it though. So I decided to do what I thought was the right thing to do. My sister flew off the handle when I told her and proceeded to file for a divorce. I encouraged her to sit down and talk about it with him. What if it was not his fault? What if the girl had indeed drugged him so she could force herself on him? But my sister told me that it was not the first time that he had cheated on her. He had once been involved with a sex worker during the 2nd year of their marriage.

He called me afterwards and confronted me and blamed me for ruining his marriage. He also told me that he had indeed cheated on her years ago but she forgave him. This time though, it was not something he had wanted to happen, but she refused to believe him now. To make me feel even worse, I recently found out that the girl he was caught in bed with, is indeed mentally unstable and obsessive and has had history of drug abuse. But no matter what I say to my sister, she will not change her mind. Now I think I believe my brother in law that he did not cheat on my sister the second time with that girl. Am I The Asshole here?

ruining (not on purpose) my sister's marriage