I have a feeling I'm going to get my boss fired for nepotism
Is this a real reason he can be fired for?
He is a total asshole for it.
If they really used nepotism and can be fired for it then you should tell on them. No one should have the advantage over other applicants.
He deserves it, my boss thinks he knows everything.
You are doing the right thing, nepotism in the workplace is very inefficient and unfair. You and your coworkers deserve a boss that came through merit, not through familial ties. Your coworkers would be proud of you for standing up for them.