A mother faked her sons' resumes after they changed their names so she could hire them at Victoria's MFB without revealing they were related.
The case cost taxpayers $400,000 and the MFB plans to refer it to Victoria Police.
"Some cases I have investigated over the years seem so unlikely you could not make them up. Except, as in this case, they did," Victorian Ombudsman Deborah Glass said on Monday.
The senior public official falsified her son's CV and coached him before the job interview, three weeks after he changed his name to conceal their relationship.
"After giving him a pay rise and moving him into a permanent role, she then hired her second son, also falsifying his CV and "interviewing" him at her home after he, too, changed his name to conceal the relationship," Ms Glass said.
The Ombudsman's office regularly encountered cases of nepotism, but they rarely displayed such calculated behaviour, Ms Glass said.
"Often the cases are minor, although wrong. Not this time, this was a case of deception where the family nest was feathered, plain and simple," she said.
The Ombudsman said the case was a reminder of the importance of people reporting something suspicious in their workplace.
The mother and her sons are no longer working in the public sector.