AITAH for siding with my fiancé when I don’t agree with either party?

Yesterday was the day that my fiancé(25NB) and I (22F), set up to go to lunch in a restaurant with my brother(27m.) Our grandmother was there as well, and we all had suspicions that she may be getting early onset dementia. After a minute, I had stepped aside to talk with my fiancé. Soon, my brother stepped in and gave his input. What he had decided was the best route to finding out, was to ask if her dead dog was doing okay. Which was just put down months prior, my fiancé and I were incredibly against it obviously. We both said we would not do it, because it was disrespectful and in my eyes fucking with her mental state. Some quick background with my brother and I’s relationship, because I think it’s relevant to understanding triggers. >!My brother and I have always had a rocky relationship, as he’s always been abusive towards me. He used to give me a look before he would do abusive things, and that was the look he gave me and them. He looked mad, and it honestly triggered me and my fiancé; as they have their own trauma that made that look trigger them.!< We all sit down, and he looks at me with expectant eyes. His face also looked like “im not going to do it, you do it. Like he genuinely looked mad at me- I gave him a look of “what the fuck, no,” in which he decided to give my fiancé a look as well. They are not good under pressure and the look he gave, subsequently made them anxious. So they ended up asking her, my grandma was obviously disturbed and she looked terrified. My fiancé then said, “Okay guys, I think she remembers.” They said it in an annoyed tone, because they didn’t want to say it at all. I do not think my fiancé should have asked or said that, and we had a conversation where they apologized and explained why it happened. They regret it deeply, because she’s become like their grandma. Who is the asshole? Am I for backing up my fiancé, and being mad at my brother for pressuring them into saying something they never wanted to? Or is he the asshole for wanting to bring it up, and then pressuring them? Or honestly, is everyone the asshole?

TLDR; My brother suggested we ask our Grandma, that most likely has early onset dementia how her dead dog was doing to see where she was at. We didn’t want to do it, and he gave us a look that triggered both of us.

!Hes been abusive before, and the look he gave was one before he’d be abusive. That in turn triggered us!< They ended up asking it, which I was upset about we’ve had a conversation where they apologized and explained. I still don’t think it’s okay, but I have an understanding of where they’re coming from. Are we all the asshole? Is he the asshole? Are they the asshole? Or honestly, am I the asshole?