Congratulations you just blew up your relationship over someone else's choice for their wedding while also insulting your potential future MIL.

Sebby told you it had nothing to do with the mom, and you just wouldn't let it go. You wanna be child free that's fine your MIL doesn't control your reproduction life.

But refusing to go to people you claim to care about and love wedding makes you an AH. They aren't saying they are gonna have kids now just they want some family who happen to be children at their wedding and unless you are magically footing the bill for it. You need to shut up, apologize and be happy for them or ya you don't have to worry about a wedding with Jen cause she'll dump you if she hasn't already.