The Johnstone family fortune was built on the back of Fulton Hogan, one of the largest privately held, vertically integrated contracting companies in Australasia.
Hanlin Johnston retains a seat on the board of the company co-founded by his grandfather Bob Hogan more than 80-years ago.
The business continues to thrive, last year lifting annual profit 6.5 per cent as the firm benefited from a growing infrastructure spend across the nation.
Net profit rose to $179.6 million in 2017 from $168.7m a year earlier, on revenue of $3.6 billion.
Hanlin Johnston also sits on the boards of vBase, Christchurch International Airport and chairs Dunedin Casinos.
Another of Mr Hogan’s grandchildren, Robert Johnstone, has a 40% stake in Island Block Farms with his wife Jean.
Jean and Robert both own a half of Glencairn Limousins, a cattle breeding operation at Glencairn near Outram in Southland.
The couple has been breading cattle for more than 30 years. The cattle breeding started as a business interest which the Johnstones ran alongside their commercial sheep and cattle operation in the Taieri Plain near Otago.