Is it rude if in-laws don't invite the spouse to family dinners?

Okay, so I’m not married but I’m just asking out of curiosity as IF I were a married person. So pretend I’m married and I have kids for the sake of a hypothetical question, lol.

So I come from a big family (5 siblings, 3 niece/nephew) and we always include a long term partner/spouse to our dinners, celebrations, get together, etc. No big deal, we feel we can spend time together and bond. My brother-in-law is always welcome to join.

My boyfriend’s family on the other hand is smaller with just 3 siblings. My boyfriend has 2 older sisters and one of them likes to make their family exclusive. They’re nice and I like them but I feel a small sting when one of his sisters constantly tries to plan “Family only” dinners with just her mom and siblings (not her step dad). Even when she wants to spend time with her father she doesn’t want her half-siblings and step mom to be around. She also doesn’t like it that her older sister confides in her uncle’s wife. Because of her actions I suspect she doesn’t really see you as family unless you are blood related.
She also invites them to dinner when I’m right there instead of asking them privately. I don’t know about you but it sucks when everyone gets an invite and not you when you’re sitting there.

Anyways, if we were married, would it be rude if she continued to plan family days/dinners (Her mother and siblings) without me?

What if she invited my kids (imagine that lol), husband, her siblings, and mom but not me?

I know a lot of people find this RUDE but a good handful believe it’s okay. It’s just hard for me to understand I guess. Again, I’m not complaining, just merely speculating and wondering.