AITA for not letting my niece be a flower girl at my wedding?

I’m 24F and I’m getting married in July. My brother has three kids, (M16)(F13)(F6) my niece (the 6 year old) was my flower girl when my brother got married last year. I also had another flower girl who was 4, she is my friends daughter.<br><br>For my wedding I have decided I do not want children involved. Both of my flower girls from my brothers wedding will be attending as guests. My friend is bringing both her children (now 5 and 7) and my brother will be bringing all three of his kids.<br><br>My brother and his wife are pissed off that I chose to not have a flower girl at my wedding and think this is unfair to my niece who is now upset that she’s not going to be involved in my wedding after being involved in theirs. I told them she’s 6 and can wait, she will likely be a bridesmaid at our wedding anyway. My brother and his wife want her to be a flower girl instead of a bridesmaid. I do not want children at my wedding as I want it to be more adult orientated and I don’t want and don’t have the budget for professional childcare at the event. They have told me I’m being selfish and ruining my nieces childhood by not letting her be involved.<br><br>AITA for telling my brother and his wife that she is not going to be involved?<br><br>Edit: I just want to point out that I did not ask her to be my flower girl at my wedding. My brother and his wife assumed she would be my flower girl because she was at his.