My 13 year old cousin is working for $5/h because he doesn’t file taxes, and I don’t know if I want to help him or not ?

My parents are uncles are co-owners of a laundromat. My cousin is 13 and they’ve been having him do maintenance and cleaning tasks for a few months now for $5 an hour. Recently, he asked for a raise to $15 and they told him that it’s only $5 because he isn’t taxable. It didn’t sit right with me, so I looked up labor laws and it’s illegal for minors (12-17) to work for less than state minimum wage. When I told him that, he asked me to not tell anyone. He said that he’s scared that he’ll get fired and that he’s grateful. On one hand, I don’t want to hurt him, but on the other hand, it’s also not fair for the other employees who are spending their time. Idk what to do and I could use some advice.