The ex is the father of a child in his wedding party. I don't think it's that much of a stretch to say, 'come join us for the wedding'. How this shows that he 'doesn't care' about the feelings of his sister's FI is odd.
I think your FI needs to stop being a little bitch and go with you.
This.
He has a chance to be supportive and classy and he's taking it out on you. He gets to be upset and say he's upset, but then he should man up. It's not like you did this on purpose.
Well, if your FI wants to prove to your family he's the man for the job, he needs to stop being a pansy and go. I understand he's hurt but his own daughter is in the wedding, you are having his child, and its his future family. For him not to go would be a big effin' deal.
This.
One way to prove your ex is a better man is gor your SO to allow his very pregnant FI to be unescorted at her brother's wedding knowing how much she wants him there.
If he's really as good a "dad" as you claim, he should be helping with the kids.
FFS, your brother is having FI's daughter in his wedding but that's not enough for him?? Simma the fuck down. Does he want a ticker tape parade for raising his FI's kids like his own? Not enough recognition to simply have those kids love and adore him?
I might want to kill this man for you. I'm just saying.