Right, context (very outing):
My fiancé and I are getting married next month.
It is a relatively small wedding with children, nearest and dearest attending.
I have not invited my "D"F as he's blocked me. This is (in a VERY short nutshell) because I pulled him up on some pretty shitty behaviour regarding my step mum/step sister. He didn't want to respond, so blocked me.
I have a total of 4 siblings (2 half, 2 step -hopefully painting a picture of the kind of guy he is). All 4 are in agreement that DF is narcissistic, controlling, has had damaging and significant affects on all of our mental health, and is probably psychopathic. Unfortunately step mum is tied to him financially, but has often spoke about how she'd be better off leaving him.
Anyway, my 2 step siblings have happily accepted invites and will be attending (despite having to conceal this from their mother, my step mum, which I understand is difficult). One said how it was for the best that he wasn't coming due to how, when he attended theirs, he tried to ruin it (which is true).
My 2 half siblings also both happily accepted, and said what they wanted to eat etc. However, they have both since said (with not much time to go) that they worry they'd upset our Dad by attending and that they feel uncomfortable about it so aren't attending. One also suggested that they were going to tell them due to how uncomfortable they were feeling (I hope you get the idea that he's quite a hostile man, so likely wouldn't flinch at the thought of upsetting our wedding day). That was quite distressing.
I think it might also be worth noting that when my half sister got married some years ago, she also did not invite "D"F, but they are now (apparently, despite constantly bad mouthing him) on better terms. My half brother celebrated this with them. They are both significantly older than me, so I did not celebrate or know as I was a child.
Am I being unreasonable to be upset by their decision to not come?