It is quite possible that their parents might be using them to get some hype on social media but it is commendable if a family is making earning by investing their time and efforts in crypto space.. Furthermore, I think it is not possible now to generate such a huge income by mining becuase Ethereum has switched over to POS from POW after the London Hardfork and now major portion of fee goes to burning mechanism and little portion goes to Miners . This mechanism  was designed to reduce supply of ethereum to increase its price.