AITA for ruining thanksgiving by telling my family that my niece and nephew are not originally my brothers kids

So my niece and nephew are not my brothers and his wife kids. My sister in laws sister and her husband “lost” the kids a decade ago. My sister in law is their legal guardian and adopted them and raised them as her own. I only know because my sister in law drunk told me a few years ago. I haven’t and don’t tell people because it’s not my story to tell. “Only the kids and my wife and I know that’s why we have been raising them as our own” she said. I feel bad for the kids and for my brother. I haven’t told my parents and siblings and I don’t think I would have told anyone but my wife. She lost her “last chance” baby on Thanksgiving. and she needed to talk to someone. I told her and said “we can’t tell anyone” and she said of course. <br><br>This year we all went to my parents for thanksgiving my sister in law and brother came a little after and I saw their “kids” and thought of my wife’s baby. She came down a little until she saw my brothers kids and lost it. Then she went on a full meltdown and told my parents and siblings that my brothers kids are not his. <br><br>My brother is livid. He has a week vacation and the kids “heard” what my wife said. My sister in law is just crying. I tried to tell my brother that I told my wife and she promised not to tell anyone and she was talking about her baby anyway. He said it didn’t matter and I should never have told my wife.