AITA for breaking up with my fiancé after he forgave my sister for ruining my career?

I (29F) had always been the responsible one in my family. I’m the oldest, and ever since I was a kid, my parents expected me to set the example for my younger siblings. As the first-born, I had to be the perfect daughter, the perfect student, and eventually, the perfect professional. My younger sister, Julia (26F), was the complete opposite. She was free-spirited, rebellious, and always found ways to get out of trouble—mostly because my parents adored her, and she could do no wrong in their eyes.

For years, I worked incredibly hard to make sure I made my parents proud. I excelled in school, went to an Ivy League university, and landed a great job in a competitive industry. By the time I was 28, I was climbing the corporate ladder and had secured a great position at a leading tech company. Everything was falling into place, and I was on track to achieve everything I had ever dreamed of.

During all this, I had been dating Ethan (31M) for three years. We met while working on a project at a tech conference, and we clicked immediately. He was smart, ambitious, and supportive of my career goals. We quickly became inseparable, and after a year of dating, he proposed. I was over the moon, and we started planning our future together.

However, everything changed when Julia decided to take a leave from college to "find herself" by traveling abroad. My parents were supportive of her decision, even though it seemed like a reckless move, considering she had no plan.

A few months after she left, Julia came back unexpectedly with news that shook me to the core. She had gotten involved in a shady business deal abroad with a group that promised her quick money. They convinced her to invest in a startup that turned out to be a scam. To make matters worse, Julia’s financial irresponsibility and careless decisions directly impacted my company. The fraudsters behind the startup turned out to be connected to a key client my company had been working with. Because of Julia’s connection to the deal, the company had to sever ties with us, and the scandal made the news, tarnishing my reputation and putting my career at risk.

The fallout was immediate. My boss was furious, and I had to do everything in my power to salvage the company's relationships and my position. My career took a huge hit, and I felt like my entire future was crumbling before me. The media painted me as part of the scandal by association, and it felt like I had worked my entire life to build a career just to have it destroyed in a matter of weeks.

When I confronted Julia about the situation, she was unapologetic. She brushed off the damage she had caused, saying that "these things happen" and that I shouldn’t be so upset. My parents, as usual, defended her, saying she was young and made a mistake, but that it wasn’t the end of the world. They expected me to forgive her and move on, but I couldn’t. I was devastated, not only by her actions but by the lack of accountability. She never took responsibility for what she did, and my parents insisted that I "stop being so hard on her."

As if that wasn’t enough, the situation put a strain on my relationship with Ethan. I confided in him about everything, expecting him to understand how much this was affecting me. However, to my shock, Ethan sided with my parents and Julia. He believed that I should just let it go because “it was just a mistake,” and that I should focus on the future instead of holding onto resentment. He also said I should forgive Julia and not let this "ruin the family dynamic." He went as far as telling me that I was being too harsh on her and that I needed to "let it go."

I was heartbroken. Ethan was the one person I thought would stand by me through this. Instead, he defended Julia, the person who had not only ruined my career but had also shown no remorse. We fought for days. I tried to explain how I felt betrayed by both Julia and him, but he didn’t understand. He kept telling me I needed to be the bigger person and not let this “tear us apart.”

After a lot of soul-searching, I made the decision to break up with Ethan. I realized that if he could forgive Julia so easily, even when her actions had jeopardized my entire future, he didn’t understand the importance of loyalty, accountability, or respect. He was willing to let go of the damage she caused just to keep the peace in the family, and that was something I couldn’t accept.

Ethan was devastated by my decision. He called me selfish for choosing my career over him and said I was being unreasonable. He told me I’d regret this decision, but I couldn’t shake the feeling that I had done the right thing.

Now, all of our mutual friends are divided. Some say I was justified in ending the relationship, that I needed someone who would stand by me in my time of need. Others say I should have been more understanding and that I ruined a good relationship over something that couldn’t be helped. My parents are furious with me for ending things with Ethan, and they’ve told me I’ve made a big mistake.

So, AITA for breaking up with my fiancé after he forgave my sister for ruining my career?