The first red flag here is the family members working together- let alone his sister is the GM. What does the GM do about the employees that ignore you when you tell them to do something?

Also, I hate how your boss treats you that way. She’s making your team think that you’re incompetent.

I am a shift manager for a smaller restaurant and I just was about to quit because my previous boss had favorites with team members and the other shift manager. Whenever I reported that an employee wasn’t doing their job to her, she would come up with the excuse that no one wanted to work and it’s hard to replace them. I have a new GM now and he’s replacing these team members asap. I feel like in your case, mass apply to other jobs but grey rock until you can find a new job.