Teen bride bans SIL's kids from wedding, 'they RUINED my engagement party.' AITA?

"AITA for telling my sister-in-law she can’t bring her kids to my wedding because they ruined my engagement party?"

My fiancé (21M) and I (19F) are getting married in a few months. We are planning a small, elegant wedding with close family and friends. From the start, we made it clear that our wedding would be child-free—not because we don’t like kids, but because we want a formal atmosphere without disruptions.

Most of our family and friends were understanding, except for my sister-in-law, who has two kids (4M and 6F). For context, SIL has a habit of ignoring boundaries when it comes to her children.

At my engagement party last year, she brought them despite the event being at a fancy venue with an open bar. Within an hour, they had knocked over a tray of champagne glasses, smeared cake all over a rented couch, and screamed through the speeches. I love my fiancé’s family, but it was embarrassing, and SIL just laughed it off, saying, “They’re just kids!”

When we sent out wedding invitations, we included a polite note stating it was an adults-only event. SIL called me immediately, asking if we could “make an exception” for her kids. I calmly explained that we wanted a child-free wedding and reminded her of what happened at our engagement party.

She got defensive, saying, “They’ll behave this time, I swear!” I stood my ground and said, “I’m sorry, but we’re keeping it adults-only.” She hung up in a huff. Then, last weekend at a family gathering, she brought it up again in front of everyone, saying, “I can’t believe you’re excluding your own niece and nephew from your wedding.

Do you hate them or something?” I firmly said, “Of course not, but this is our wedding, and we want it to be the way we planned.” She got even more upset, saying I was being unreasonable and that “family should come first.”

Now, my fiancé is caught in the middle. He supports me but also doesn’t want to create a family feud. His mom has even suggested that we “just let it go” to keep the peace. But I feel like if I cave, it’ll send the message that our boundaries don’t matter. So, AITA for refusing to allow my SIL to bring her kids to our wedding after what happened at our engagement party?

Here's what top commenters had to say about this one:

Huge-Excitement-8798 said:

NTA. And tell your spineless fiancé that if they show up, you are leaving. It is that simple. And you will make a scene as well.

sparkledcupcake said:

NTA it's your wedding and SIL already showed she can’t control her kids, and you have every right to want a peaceful, elegant event.

TheInternetSleuth04 said:

NTA, If your soon-to-be SIL can't keep her kids under control after you made it clear it was child-free and she ignored it. I would tell her that due to her disregard for your wishes at your engagement party, it's either she shows up without the kids or she can't come to the wedding. Sincerely someone who had something similar happen at my wedding last year.

Difficult_Mood_3225 said:

Please postpone and live a little. Especially given how spineless your fiance is being. NTA except to yourself if you marry this man now.

Altruistic-Bunny said:

The SIL can let it go to keep the peace. A better response is "the venue is not child friendly" but I could understand "your brats caused extra breakage and cleaning fees because you do not watch your kids." Your fiancé needs to make it clear to his family that BOTH of you want a child free wedding. If he does not stand up, then they will see it as you "controlling" him. NTA.

Ray_3008 said:

Don't marry him. She will bring her kids and your fiancé isn't supportive to you. His inability to side you clearly means he is siding his family.