Usually, people working in their family businesses are employed by their parents, a sibling or a grandparent. Therefore banks are not sure how reliable an employment letter, payslips or other documents are to prove their income.
They manage their risk by asking for additional documents that are not required by people who don’t work for a relative’s business.
As part of their normal employment verification processes many banks complete an ASIC search on the employer to confirm if the directors and shareholders of the business are related to the borrower.