AITA for not allowing my other niece-in-law to be in the bridal party as a flower girl?
Edited with all the information I put in the comments.
My fiancé (30 M) and I (25F) are getting married in November 2026, but what should have been an exciting few months leading up to our wedding has turned into a major family rift involving his twin brother, his sister-in-law, and their daughter.
I'm wondering whether I'm in the wrong, so I'm going to explain the timeline as clearly as possible.
Some background
My fiancé and I started dating in May 2024. I have a son (6 years old currently) from a previous relationship who is currently suspected of having autism and ADHD, although we are still going through that process.
I first properly met my fiancé's twin brother, his wife, and their daughter in August 2024, when we were all at my future mother-in-law's house for dinner.
Unfortunately, there was already an issue between the kids during that first meeting.
Their daughter became angry because my son was playing with a toy, even though she hadn't been playing with it then.
I understood that kids have disagreements, especially because their daughter is autistic and my son is also suspected of being neurodivergent, so I didn't want to make a big deal out of one interaction.
However, it became the start of an ongoing pattern.
My fiancé and I got engaged in December 2024, just over seven months after we started dating. When you know, you know.
Around Christmas that year, we started asking family members to be part of our wedding party.
My sister agreed to be my maid of honour, and my best friend became my bridesmaid. My fiancé asked his twin brother to be his best man, even though my fiancé hadn't been a best man or groomsman at his twin's wedding.
He asked him because he was his twin brother, and he trusted him and wanted him beside him on one of the biggest days of his life.
We also asked both of my fiancé's nieces to be flower girls.
My fiancé's sister said yes for her daughter.
My fiancé's SIL said no for her daughter.
Their daughter had been diagnosed with autism before I joined the family, and my SIL explained that she didn't think her daughter would cope well with being a flower girl because of the number of unfamiliar people and the public nature of the wedding.
We completely understood.
There was no argument. We didn't pressure them or question their decision. We respected the answer and continued planning.
So, our confirmed plan became my fiancé's sister's daughter as our flower girl and my son as our ring bearer. They would walk down the aisle together using bubble guns rather than throwing petals because of our venue's restrictions.
Things between the kids didn't exactly improve.
We didn't see my fiancé's twin brother and his family very often after that.
The next significant time was Christmas 2025.
At that gathering, their daughter essentially ignored my son. She played with the other niece but not with my son or any of the other cousins.
Again, I didn't start an argument. I wanted to keep the peace and understood that children, particularly neurodivergent children, can have their own social preferences and boundaries.
Then we saw them again in March 2026.
The kids were playing with slime when my son accidentally mixed some of their daughter's slime—just a small amount.
She responded by hitting my son.
I immediately stepped in and calmly explained the situation to my son. He hadn't intentionally ruined anything, and I wanted to explain why she was upset and what had happened rather than yelling at him. The slime was an easy fix; I separated the two slimes again.
My SIL, however, yelled at my son over it.
That was a major issue for me.
My son is suspected of having autism and ADHD himself, but even putting that aside, I don't believe yelling at a child over an accident, when he was already upset by the situation, is an appropriate way to handle it.
I had already stepped in as his parent and was calmly explaining what had happened and why his cousin was upset. I felt the adults could have handled the situation calmly instead of my son being yelled at.
I stood up for my son, and my SIL didn't appreciate it.
Then came the flower-girl argument.
In April 2026, my fiancé received a message from his twin brother asking:
"Can our daughter be a flower girl in the wedding?"
We were confused.
We had already asked them in December 2024, and they had declined.
By April 2026, this wasn't an early-stage wedding where we were casually discussing ideas anymore.
My Grandmother and my parents had already paid our first venue deposit, and we attended our first venue meeting, where we went through the wedding timeline, structure, and guest count, including the wedding party.
Our bridal party was confirmed. The processional had been planned. Our flower girl and ring bearer already had their roles.
So we said no.
It wasn't because we hated their daughter.
It wasn't because she is autistic.
It wasn't because we were deliberately trying to exclude her.
We had already offered her the role. Her parents declined it. We respected their decision and planned our wedding accordingly.
Apparently, that wasn't acceptable.
My fiancé's twin brother then stepped down as best man.
That genuinely hurt my fiancé.
This wasn't just some random groomsman dropping out. This was his twin brother.
My fiancé had trusted him to stand beside him on his wedding day, and suddenly he was pulling out because we wouldn't change an already established part of the wedding.
My fiancé was incredibly disappointed and hurt because he had trusted his twin brother to be there for him on one of the biggest days of his life.
He eventually asked his younger brother to become his best man instead.
At that point, his twin brother said that he, his wife, and their children would still attend the ceremony but not the reception.
We accepted that too.
Around this time, things between my SIL and me became even worse.
After we refused to change the flower-girl arrangement, she started repeatedly calling, texting and leaving me voicemails. She called me a bridezilla and a bitch because I wouldn't put her daughter into the bridal party. We eventually found out afterwards through my fiancé's sister that they never even asked the niece if she wanted to do it. Apparently, the niece didn't want to do it at all and wanted to enjoy the wedding.
Eventually, I blocked her.
I was attending university classes and getting calls from her throughout the day, and I wasn't going to continue dealing with it.
However, our problems go back further than this.
I have repeatedly tried to keep the peace with her because she is my fiancé's twin brother's wife, and I didn't want to create family drama. Despite that, I don't feel she has treated me particularly well.
There have also been several occasions where I felt like important events in my life somehow became about her.
At my engagement party, she was pregnant at the time, and I felt that attention repeatedly had to be redirected toward her and her pregnancy. The twin brother also made inappropriate comments toward me, especially after finding out he shared the same name as my father and said that I could call him "daddy."
Something similar happened around my 25th birthday, when once again I felt like an event that was supposed to celebrate a milestone in my life somehow became focused on her.
Despite all of this, I have tried to remain civil because she is part of my fiancé's family, and I never wanted my issues with her to damage his relationship with his twin brother.
There's also some strange history that I learned about later. When SIL originally met my fiancé and his twin brother back in high school just over 10 years ago (I would've been just going into year 7), she apparently had a crush on my fiancé first. He wasn't interested in her and was introduced to his twin instead. They eventually got together and married.
I don't know whether this has anything to do with how she treats me, and I'm not claiming it definitely does, but learning about it made some of our interactions feel a little more uncomfortable in hindsight.
Now they aren't coming at all.
Fast-forward to August 2026.
My fiancé and I were out at an event when he suddenly received a Facebook Messenger message from his twin brother after months of very little communication.
It said:
"Hey, just wanted to let you know that I won't be able to make it to your wedding after the recent events. I think it's best that I don't come. You will always be my brother, but I have to do right by my family, and obviously you will do the same."
So now they aren't attending at all.
Not the reception.
Not even the ceremony.
My fiancé is genuinely hurt.
This is his twin brother - someone he grew up with, shared a room with, shared his childhood with, and trusted enough to ask to be his best man.
First, his brother stepped down as best man. Then they decided to attend only the ceremony. Now, three months before the wedding, they've decided they won't attend at all.
What makes this situation even stranger is that the rest of my fiancé's family supports us.
His family knows what happened and, rather than blaming us, they've supported my fiancé and me. They also don't agree with the way his twin brother has handled everything.
That support has been reassuring, especially for my fiancé, because this situation has understandably hurt him.
From our perspective, this escalated because we declined to offer the wedding role we had already offered her almost two years earlier, and they declined.
I also want to stress that I don't blame their daughter for any of this.
She is seven years old and autistic. She isn't responsible for her parents' decisions or how the adults in the family communicate with one another.
Likewise, I don't expect her to behave exactly like a neurotypical child, especially when my own son is suspected of having Autism and ADHD. I understand that both children may experience emotions, social situations, boundaries, and conflict differently.
My problem is with how the adults have handled everything.
If they had accepted our original offer in December 2024, she would have been a flower girl.
They said no.
We respected that answer and planned accordingly.
Then, after deposits were paid, the venue meeting had happened, the wedding timeline had been discussed, and the bridal party was established, they changed their minds and expected us to change those plans.
When we didn't, my fiancé lost his original best man, and now his twin brother has decided not to attend the wedding at all.
Part of me feels guilty because I know how much this has hurt my fiancé, and I never wanted our wedding to cause a rift between him and his twin.
But another part of me feels like we didn't create the rift.
We asked their daughter to be involved. They declined. We respected their decision. They later changed their minds, and when we didn't change our already established wedding plans to accommodate that, the situation escalated.
Even with everything that has happened between SIL and me, I have tried to keep the peace because I never wanted my fiancé to lose his relationship with his twin brother over me or the wedding.
But at this point, I'm questioning whether I should have just said yes in April to avoid all of this.
So, Reddit, AITA for refusing to add my fiancé's niece as a flower girl after her parents originally declined the role, which led to my fiancé's twin brother stepping down as best man and eventually refusing to attend our wedding?
Just a little note on the side: The SIL also called up our venue to ask if our wedding was still happening because they hadn't received the invite (we hadn't sent them out at the time), and tried to tell my fiancé's parents that we must've eloped in private without either family and are not getting married at all.