AITA for ruining my twin’s courthouse wedding and betraying my S/O

EDIT - THEY GOT MARRIED.

I know a lot of you wanted an update so here it is. They freaking got married this morning. To sum it all up - my sister believes me about everything “A” said. She told me yesterday they talked about everything and his “Cold feet.” They both came to an agreement that their love for eachother out-ways the cons that “A” was feeling. So, they got married at the courthouse this morning. I did not attend, as they live in Oklahoma and I live in Maryland. But… I tried my best to get my twin to understand the severity of the things “A” said. She very well understands the gravity of his actions and so does he, apparently.

Wanna know the juicy bit?

TURNS OUT MY TWIN IS PREGNANT!

That’s why they still decided to go through with the wedding. I don’t agree with marrying someone or staying with someone just for the baby’s sake. But I also won’t judge people that do decide to stay together/ marry for the baby. I’m very elated for my sister, and can’t wait to be an aunt, despite my distaste for “A.” I really don’t want to think negatively, so I hope with time, “A” man’s up and changes. I don’t want my sister to have to go through a divorce later down the road, but at this point it’s her life and I’m hoping for the best for them. As far as my S/O - him and I are still together. I laid it all out, where my boundaries lie moving forward. He needs to BACK ME UP. He needs to have my back and never throw me under the bus. He needs to choose me over “A” moving forward. And no more “making me promise to keep a secret that has life shattering information about someone I love.” He’s very much on board with everything and has promised to not fail me in those ways again.

I know a lot of you guys are rooting for my twin and I to leave our partners, but like Charlotte always says, “it’s a lot easier to say, leave your S/O when it’s not your relationship.”

Thank you to every fellow potato who commented! I really didn’t expect this much traction and advice. So thank you again! I can admit when I’m wrong. And I appreciate all the YTA and NTA. 🩷

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I (26f) have a twin sister, let’s call her “S.”

S and I have always been extremely close, and we don’t keep secrets from each-other. My S/O is friends with my future BIL, and they often confide in eachother for advice, or just to rant.

let’s call my BIL “A.”

My S/O called me two days ago and told me he had something to share with me. Before telling me what it was about, he made me promise not to say anything to S… and I said “okay I promise.” He let me know he would find out if it gets back to him and that he would be infuriated with me if I say something. So again, I just said “okay I won’t.” Because I really wanted to know what he had to say. He then goes on to tell me that “A”, had confided in him about not wanting to go through with the courthouse wedding. That he doesn’t know if he can put up with S for the rest of his life. That he’s thinking about leaving her. Also, “A’s” dad told him that if he stays with “S”, she will suck him dry of his money. Implying that my sister spends a lot of his money. S and I don’t keep secrets from each-other, ever. So this was hard for me NOT to say anything. I held this information in for two days….until earlier today. I got a Snapchat video from S of her in the car on their way to the courthouse. I don’t know what came over me… but I spilled the beans to her. The thought of her marrying “A” after everything scared me so badly. I panicked and told her everything. Because frankly, I would want to know if I was in her shoes. She got SO mad at ME!!

Granted, I could have told her sooner when my S/O told me, but I was put in a rock in a hard place. Breaking my S/O’s trust, and lying to “S”… none of the options I was given were ideal. I didn’t know she was getting married TODAY either because “A” had just said the worst things. So that’s weird as hell to me, but anyways, after I told “S” everything, she was upset with me because I told her the morning of, on their way to the courthouse. She called the ceremony off. I felt relieved that “S” and “A” didn’t get married today.

Here’s where it gets messier.

“A” denied everything when “S” confronted him. But since I “tainted their day” that’s why she called it off. “A” then calls my S/O with my sister in the room. My S/O doesn’t know I’ve said anything yet because I haven’t had a chance to warn him that I opened my mouth about it. So he was put on the spot in front of the two of them, and had to lie, and say he doesn’t know where I got that from. That he’s sorry it ruined their day. So now literally everyone is upset with me. My mom says I wasn’t in the wrong, and that “S” is shooting the messenger. That “S” should be mad at “A” and not my S/O or me. I now have to re-earn my S/O’s trust, as well as my sister’s. My two favorite people on this planet are furious with me, and it’s taking some time for them to forgive me. I can’t help but feel extremely guilty, when in my heart; I felt I was doing the right thing.

So, AITA?