Circumstances surrounding the death have remained a mystery for two years, with Detective Inspector Paul Borrell saying soon after the death that preliminary toxicology reports left "some unanswered questions which police are working to clarify".
Tasman District acting crime manager Detective Senior Sergeant Jacqui Corner said the recent arrests came as the result of a meticulous investigation over two years by Nelson detectives.
"This is a timely reminder that police are prepared and committed to continue and pursue criminal investigations long after an event in pursuit of the truth and to bring those who have no regard for the law to account," she said.
"It is virtually two years to the day since Harris' body was found.
"Our staff have been extremely patient and professional in gathering sufficient evidence to bring this matter before the court."
Corner said police still have a long road ahead as they take the matter through the court process.
"But my hope is that the tenacious work of our investigation team will bring some closure for Harris' family."
The woman is to appear in the Rotorua District Court tomorrow and the man will appear in the Nelson District Court on Monday.
Harris' son, Jade Harris, cut off his home detention bracelet in February of 2016, blaming the trauma of having his mother "murdered" two weeks earlier.
He was sentenced in the Masterton District Court to seven months' imprisonment after the judge cancelled his home detention sentence.
Police are asking for anyone with information in relation to this investigation, who hasn't come forward, to make contact with the Nelson CIB on 03 545 9679, or anonymously via Crimestoppers on 0800 555 111.