I'm the product of my mom having an affair. Fortunately, my dad decided to forgive my mom and keep me. And I had a pretty good upbringing, but I don't really look a lot like the rest of my family. And I did ask questions of why I'm the only redhead. When I was young, my mom took me out for ice cream and introduced me to my biological father. She said she felt I was old enough to know the truth and explained about her affair. While also, A, making me promise I won't tell my sister and B, hammering home along with my biological father that he never wanted to be a part of my life and didn't want me. It was a lot, I won't lie. But I learned to suck it up and move on with my life. Fast forward to the present, my big sis has always gravitated towards older men and, two months ago, shared a picture of herself with her new boyfriend, who to my shock turned out to be my biological father. I debated what to do for a couple of days, then ultimately decided she needed to know the truth and told her. My sister did not take it well and dumped him, but she wasn't angry with me. Honestly, by now, she's kind of amused, says that since she begged my dad, she's my mom and has extra power to boss me around. My mom, on the other hand, was furious. She says I divulged something that wasn't my secret to share and that I had no business telling anyone, that since my biological father isn't related to my sister, it didn't matter if he dated my sister and it wasn't like they were talking marriage anyway. It's been two months and she's still angry, still snide, calls me a traitor and finds an excuse to make loud comments about how I can't be trusted with anything private or important, so beware. At the time, I thought I was doing the right thing, but I've never seen my mom this angry before and she's sustained that anger for two solid months, so I'm starting to worry. Did I actually do something really shitty? Am I the asshole?

Mom's the one that did the shitty thing by cheating on your dad. You just helped your sister not get into a weird relationship. Can you imagine if she had brought him around for like Christmas or Thanksgiving?