The two people killed in Hāwera on Monday morning have been named by police.
They were father and son, Stephen John Frost, 55 and Regan Frost-Lawn, 15.
They were found dead at the Hāwera property after emergency services were called at around 2.50am on Monday.
Police say post mortems commenced yesterday.
A 21-year-old man was arrested at the scene "without incident" and has now been charged with murder.
He has appeared in the New Plymouth High Court and will reappear on 9 February.
He has interim name suppression.
Police say the investigation is continuing and includes an ongoing scene examination at a Hāwera property.