If the family business didn't exist, housing and food are a responsibility of the parents regardless of the kid's working status, until that kid is able to be independent. Pushing the kid into a family business does not entitle the parents to exchange their responsibility for payment. If that's the way the situation is approached, then the kid must be kicked out of the household first, then offered the opportunity to work for those things when he's already out on the street. That is the level of formality required to make such an arrangement.

If the parents are willing to make that unreasonable decision, and the kid is able to navigate through their anger over the decision being made, only then is the ground set for making a business arrangement for the kid's survival. If they can manipulate the kid's desperation enough to offer him survival as payment, then the weight of the situation will be clear to the kid and he can make an informed decision.

That said, depending on the age of the kid, parents have a legal obligation to continue supporting them until that obligation no longer applies. Kicking the kid out before then is criminal, and kicking them out after is cruel despite no longer being criminal. Only when the kid is earning enough money to fund his own independence, that's when kicking them out becomes reasonable. If you don't pay him any money in a family business situation however, then you'd not only be committing to the cruelty of kicking him out with no means of independence, but you'd be perpetuating him to a life of extreme poverty at the edge of basic survival.

It is quite plainly irresponsible of the parents to fail at paying their kid for work in their family business. If it's not illegal (which depends on where you're from and what their law on employee compensation are), it's most certainly still immoral. The kid would be better off in the long term being thrown out like garbage to find his own way through minimum wage labor while staving off homelessness and starvation.

Regardless, a family business is intended to be handed down to support the next generations. If you're handed a business that didn't support you financially in the past, the business didn't do what it was intended to do and the business has failed. A family business would serve better dying off if the entire family didn't benefit from it as the business model is intended to do.