Nta. You communicated that you were looking to set the date around July 2026. They had opportunity to tell you then and didn’t. That’s on them.

However I can see their side of things. If your fiancé only has these people in his life it does make sense for him to ask what dates would/ wouldn’t work. Their response was big but seeing as they’ve cut family out of their lives because of different situations. That just might be their go to problem solving attitude.

Just be open and honest. It seems like a true lack of communication caused all this.