AITA (Fanfic writes)

Am I the asshole for revealing that my sister's dad isn't her biological father?

(Twilight; Bella Swan Sibling)

I, 17 female/male/enby, attending my, 18 female's, wedding. She and her husband had just graduated from high school a month prior and immediately got married (they had been engaged since the middle of senior year).

My sister's "dad" Charlie for privacy was asked to walk her down the aisle and give her away.

I was aware that Charlie was not my sister Bella's biological father as he was infertile and had been after an accident in one of his middle school football games. My mother, Renee, had an affair with his best friend, Waylon, and had my sister. Charlie knew that Bella wasn't his but tried to be a father to her since his Waylon wouldn't step up to the plate. A year later my mother divorced Charlie and remarried to Phil my father and had me 6 months later.

I assumed that my sister knew about all of this as she always called Charlie by his first name and never "dad". After the ceremony I pulled my sister aside, and congratulated her as well as tell her that I was proud of her for including Charlie. My sister was confused and asked "What are you talking about?"

I confusingly blurted out "You know, since Charlie isn't you biological father you still asked him to give you away...." My sister's face morphed into to one of shock and she yelled out "Charlie isn't my dad?!" I froze in shock as I realized that I just revealed a huge secret. My sister started yelling at me and demanding answers while I stammered out gibberish.

This drew the attention of the wedding guests and our parents who made their way over to us. Renee asked what was going on and my sister went off on her and Charlie for not telling her the truth.

Long story short, the wedding was ruined and now my mother and father are calling me an asshole and saying that I should've kept my mouth shut while Charlie says that it was an honest mistake and that he thought that Bella was aware as well.

But I can't help but wonder.....am I the asshole?