Michael Erceg's brother has been denied access to documents that would reveal who got what from two trusts set up by the late multimillionaire and liquor magnate.
Erceg was the founder of ready-to-drink beverage company Independent Liquor and was estimated to be worth $620 million at the time of his death almost a decade ago.
Members of his family have feuded ever since.
Last year his brother, Ivan, took court action to see documents associated with the two trusts, which were wound up in December 2010 with Ivan - a beneficiary of both - receiving no distributions.
Before being declared bankrupt earlier that year, Ivan ran the now-sunk Sensation Yachts - a company which specialised in multimillion-dollar vessels for wealthy customers.
His bid to see the documents was opposed by other trustees, Michael's widow, Lynette, and lawyer Darryl Gregory, with Queen's Counsel appearing for both sides in the High Court at Auckland in December.
The arguments during the hearing were subject to strict confidentiality orders imposed by Justice Patricia Courtney.
In her judgment, however, she says there was "distinct unease about the ramifications for family relations" if Ivan had access to the documents.
"The category of documents being sought would disclose the identities of other discretionary beneficiaries and the nature of distributions made," Justice Courtney said in a decision released this month.
Although Ivan had raised concerns around the administration of the trusts, Justice Courtney said nothing specific was identified. "Mr [Ivan] Erceg's main complaint seems to be simply that he has not received any distribution from the trust assets."
The "weight of the evidence" was that Michael had intended the trusts would be administered in confidence and he did not want his family members who might benefit from them to have information on this.
While Justice Courtney said she would have exercised her discretion and declined ordering the disclosure, she did not need to as she found Ivan did not have the standing to bring the action in the first place.
That was because Ivan's right to seek disclosure of trust documents was vested in the Official Assignee upon his bankruptcy and he did not regain the right upon release from bankruptcy last year, the judge said.
Ivan, according to a separate High Court decision last year, was acting as a family adviser to his mother, Millie Erceg, who in 2012 brought action against daughter-in-law Lynette and Gregory as trustees of the Erceg Family Trust.
The proceeding related to the Erceg estate but the details remain secret and were subject to suppression orders during an earlier hearing.
Millie, now in her 80s, also brought civil proceedings against Lynette Erceg and Gregory as trustees of the Acorn Foundation Trust.
This trust sold its shares in Independent Liquor for a "substantial sum", according to the ruling.
Michael Erceg, who was 50 when he died, was piloting his helicopter to Queenstown with a friend when the craft disappeared near Raglan in November 2005.
The wreckage was found about two weeks later in dense bush, and both men are believed to have died on impact.
Independent Liquor was then put up for sale and bought by private equity interests, Lynette, and others. It was sold in 2011 for $1.5 billion to Japan's Asahi Group Holdings.