I am shocked. I have never ever heard of anyone of any faith or no faith not allowed to attend a funeral or shiva or anything else related to a Jewish person passing. There are no Jewish customs prohibiting non Jews taking part in shiva, none, no such rules (they don’t have to participate but they aren’t to be deliberately excluded). I’d say your ex and his family made some stuff up for whatever reason. Not good. How do you say to your spouse not to come? Anyone can attend anything. Especially once’s spouse.

Glad to hear he is an ex.

I’d say it does sound like there would be some difficult emotions around rituals of death if you are repeatedly slighted like this by your own family, even a spouse! I am frustrated on your behalf. Stick with your kind hearted brother and your son. The rest of them can go you know where