The wider Bain and Cullen families are angry David Bain did not defend his family's reputation, disappointed with the jury at his retrial, and believe the prosecution case hit on the truth of the matter.
Comments to that effect from Robin Bain's brother Michael, on radio yesterday, are backed by the sister of Robin's wife, Margaret Cullen Bain, who says her family agrees with the Bains.
Michael Bain told Radio New Zealand he was upset with his nephew David, who was acquitted in June this year of the 1994 murders of his parents Robin and Margaret and siblings Arawa, Laniet and Stephen, following a three-month-long retrial.
"Yes, I am angry. I'm very sad he allowed these allegations against his father... during the court proceedings."
Mr Bain's comments expanded on an article he wrote which was published on Monday.
The article was the first time the family had spoken publicly about the murders and in it he expressed dismay at the way his brother and his family were "vilified" at trial and insisted Robin Bain was a "loyal, peaceful and thoughtful" man and "no killer".
He said yesterday that there appeared to be no forensic evidence incriminating his brother presented at the trial. Rather, the evidence that was presented was all based on hearsay.
"I was incredulous the jury couldn't see through that."
Although the defence argued the police had done a shoddy job, the family did not think the police had erred at any stage.
"The family believes the police did a magnificent job. We believe the truth of the matter was presented in the prosecution case."
He stopped short of alleging his nephew David was the killer because "he is my brother's eldest son and still part of our family" and because he did not want to be in contempt of the court.
He said the family had not tried to contact David since the retrial, but would not reject him if he got in touch.
David Bain supporter Joe Karam told the The New Zealand Herald David Bain had approached the family several times over the years and they had not responded.
Michael Bain was living in "denial", and he questioned how well Mr Bain knew his own brother, as they had seen each other only a very few times in the eight years before the Bains' deaths in Dunedin.
The defence evidence at the trial about Robin Bain's behaviour, work, personal hygiene and dress came from people who worked with him daily, Mr Karam said.
Michael Bain said he had spoken out about the tragedy in the hope that doing so would persuade people to view the matter in a light other than the how it had been presented over the past 15 years.
When contacted, Margaret Cullen Bain's sister Val Boyd, of Wellington, said her family "absolutely" agreed with everything Michael Bain had written and said.
She declined to comment any further. Another sister, Jan Clark, of Dunedin did not return calls.
