I'm a little angry at my family for inviting me for lunch  with only 12 hours of notice? It happens constantly some random sunday a month or so
Why would they do that time and again?
They have no respect for my time.
I would be upset too, how do they know that you do not have plans already. They should be more respectful and give you more notice.
They should just stop inviting me to their lunches.
It okay to tell them that, they should learn to respect your time or not expect you to come.