AITA for confronting my MIL about going behind my back with my kids?
I've been with my husband for a total of over 15 years now, married for 2. I moved into his families house with him when we were both 16 and developed a close relationship with his mom. So close to the point that I even call her mom. My husband has an older sister and a younger brother. His younger brother is married, but me and his wife never got along. We've had a lot of issues in the past (years ago) and it got really bad to the point where my husband and I moved out of his parents house and cut off contact with everyone.
Fast forward to present time, his brother's wife has tried to make amends with me multiple times over the years since it's been years and we both have kids now, like buying me/husband and our kids gift for Christmas, reaching out via my MIL etc. But I wasn't having any of it and refuse to have any contact with her, or allow my kids to have any contact with her kids (she has 3).
My MIL HATES that we don't get along and that every holiday she has to have two celebrations since she can't have everyone together. She tried to stay neutral and not take sides but it's obvious that she just wants her family to be together again.
my (5F) and (1F) daughters stay with my MIL from Monday-Friday while my husband and I work. They're at my MIL's house more than they're at ours. A few days ago my eldest daughter was talking to me about her week with grandma. She said her and her sister met some new friends this week and started giving the names of her 3 cousins, the ones we don't speak to. Apparently my MIL went to visit my BIL and his wife/ their kids and took my kids with them, since they're with her all the time. MIL never mentioned this to me at all, and I presume wasn't planning on telling me.
So I confronted my MIL and asked why she did this and didn't tell me? She explained that its been over 10 years and she is sick of keeping her grandkids away from each other and having this divide in the family. She said the fact that her sons don't speak has been killing her for years, and she doesn't think it's fair that my kids and my BIL's kids have never met due to some stupid drama that happened years ago. I told her I don't want my kids having anything to do with my BIL, his wife or their kids and that she needs to respect this or I will find somewhere else to leave my kids during the week. She was obviously upset about this.
I was talking to my SIL (husbands older sister) and my niece about this and to my surprise they think this is kinda an AH move on my part. They said that they don't think it's fair that my kids won't get to ever build a relationship with their cousins due to some drama that happened over 10 years ago. They also said my MIL is doing my husband and I a favor buy watching our kids Monday-Friday without getting paid a cent, and that I shouldn't give her such a hard time
Was this an AH move on my part?
EDIT: I couldn't fit an explanation due to the word count but the drama that occurred between my SIL and I was that she used to constantly talk shit about me and make comments behind my back. One day I overheard her talking shit about me to my MIL and I confronted her. She tried to deny what she said and played that victim. Ever since then I cut ties with her and my BIL and want nothing to do with them. My MIL has always tried to stay neutral.