Both died in early September and their deaths have both been referred to the coroner by police, who believe they were victims of fatal doses of synthetic drugs.
Police allege Uritua supplied both Makikiriti - who had given birth to her third son just two weeks earlier - and Taneao.
He is facing two charges of selling or supplying a psychoactive substance.
Mitchell Moss and another man who has interim name suppression have been charged alongside Uritiua.
It is understood police alleged the pair supplied Uritua with the drugs that he gave his sister and cousin.
Uritua appeared before Judge Josephine Bouchier just after 10.30am today.
He did not enter a plea and was remanded on bail until his next date.
His lawyer Michael Ip said he had only just received the disclosure documents - effectively all of the evidence police have against Uritiua - yesterday.
Isitolo Uritua in the dock at his second court appearance following the deaths of his sister and cousin. Photo /Greg Bowker
He sought a remand to familiarise himself properly with the police case.
Ip said Uritua had no comment to make about the charges.
Uritua appeared in court alone but it is understood he is being supported by his family.
They do not believe he is responsible for the deaths.
A spokeswoman told the Herald they did not want to comment.
Effects include, but are not limited to: decreased motor coordination, fast or irregular heartbeat, disassociation, dizziness, paranoia, psychosis.
Use of synthetic drugs in New Zealand has also been linked to renal failure and heart failure.
(Source: alcoholdrughelp.org.nz)
Where to get help
If you, or someone you know, is using synthetic drugs, police urge you to stop immediately and seek help if needed by contacting your local GP or by ringing the Alcohol and Drug Helpline on 0800 787 797 or text 8681 seven days a week to speak to a trained counsellor.
If you or someone else is in immediate danger call 111.
