Are you automatically invited to family gatherings?

I keep having this argument with my fiancée. His grandma is basically our neighbor and today she is hosting a “happy hour” and she invited my fiancées mom and his dad (among other family). His grandma never sent a text asking us to come over or nothing.

He thinks because we’re basically neighbors AND family we are automatically invited to all their gatherings including any gatherings his mom hosts (but doesn’t invited) only because we’re family.

So my question is, do you still need an invitation to attend a family gathering? Or are you automatically invited because it’s family and you can show up anyway?