To not go to a wedding if husband is not invited

[Anuta77]

My ex sister in law (separated from her brother 12 years ago, but kept in contact because we used to have a good relationship and for my son).
My ex, her brother, has been married for a few years and even had another child. He's not really involved with my son, so no loyalty issue there.
The ex SIL met my husband a few times and I never noticed any issues between them.
Today she sends me an invitation for her son's wedding (my husband even translated some documents for them) and asked to confirm my presence with my son. I'm sure it's a small event. No mention of my husband.

How do I handle that? Is that normal? Should I just assume that my husband is invited? I'm sure my husband will not care much, but I can't help but think that it's not ok. AIBU?

P.S. We are not from the UK and ex SIL is latin.

That makes absolutely zero sense. People don’t need to demonstrate that they ‘believe in’ the principle behind whatever you’re inviting them to in order to merit an invitation. Otherwise no one who wasn’t a paid-up C of E member would be invited to a church wedding in a C of E church, no one childfree by choice would merit a baptism invitation, no one who’d dropped put of school would be invited to a graduation.

On several occasions now I have come across Latin (by which I really mean Catholic) families where divorce is still such a taboo that you basically have to pretend it never happened and the couple in question are still married.

No-one is actually fooled by it, but it's definitely a thing and the presence of a new spouse puts paid to the lie.