Garda Commissioner Drew Harris has agreed to set up a serious case review of the probe into the murder of Clodagh Hawe and her three sons.
Clodagh (39), Liam (13), Niall (11) and Ryan (6) were killed in their home near Ballyjamesduff in August 2016 by Alan Hawe, who took his own life.
This new development, confirmed by gardai, follows a meeting between Drew Harris and Clodagh's family at Garda Headquarters in Dublin.
"Commissioner Harris told the family he has appointed Assistant Commissioner Barry O'Brien to conduct a serious case review of the investigation," a spokesperson said.
"The review team will take a number of weeks to establish. Commissioner Harris said the family will be kept informed as the review progresses."
The review will look at the garda response to the family's deaths, rather than the lead-up to the murders themselves.
Following yesterday's meeting, Clodagh's mother Mary and sister Jacqueline told members of the media that they welcomed the decision.
"We have had a very constructive two-and-a-half hour meeting with the Garda Commissioner," said Jacqueline Connolly. "He has agreed to conduct a serious case review. We look forward to being appraised of that process in two weeks time.
"Once again, we would like to thank the media for the respectful coverage around Clodagh, Liam, Niall and Ryan and for the support we have received from everyone around the country."
Gardai described the meeting as being conducted in a "dignified manner".
"It is welcome that the family found it productive and it helped provide clarity for them on some matters," a spokesperson said. "Commissioner Harris provided the family with information on the criminal investigation undertaken while also respecting the data protection rights and confidentially of those individuals who had given statements in the course of the investigation."
Earlier this year, the family was refused copies of the garda files from the original investigation into the murders. The have since been appealing for a new and full inquiry into the murders and to be given access to the garda files. They are also calling for a review of Ireland's inheritance law, in which a spouse can benefit financially from domestic murder.
In an interview with the Sunday Independent, Ms Connolly said that in the days and weeks after the killings, they slowly started to learn that they had few rights.
This began when they moved to have Hawe exhumed from the grave he shared with Clodagh, Liam, Niall and Ryan.
"Of course, when we tried to have the body exhumed we learned that we had no rights. It would be the Hawe family that would have the ultimate say whether there would or would not be an exhumation," she said.
Since the inquest, Clodagh's family have learned from the notes of his counsellor that Hawe had been viewing pornography at work and was experimenting with cross-dressing.
He had stated he had been caught "red-handed" and Ms Connolly and Ms Coll want to know what that refers to.