Short advice:
Do NOT apply for your parents or your brother at the moment. Their financial situation is a mess. It would seem like they are tax evaders who are paid cash, but they do not file their tax returns.
For their own good, they would want to sort out their financial situation ASAP before the tax authorities start investigating. And, travel abroad will only speed up this investigation.
With all financial transactions linked to core banking, they are likely to face tax scrutiny considering they have stores and businesses.... and they have possibly not applied for GST registrations.... do not have credit cards.... do not have no loans or mortgages.... all cash payments (not sure how they are able to get away with this)