The family member, who said he was referred to as a "brother" despite not being blood brothers, said he used to smoke synthetic cannabis with the man often when he lived in Rotorua.
The family member said he had since moved to the South Island to "get clean", which he said he had done.
He told the Rotorua Daily Post yesterday through tears he often told the man to give the drug up, even when they were both using it.
"I tried (to make him stop) ... But you can't stop anyone from doing it ... When you smoke synnies (synthetic cannabis) you are a fiend. You will steal off your dying grandmother to feed your habit.
"That synthetic s*** has taken over the whole P industry. I smoked P for 13 years and even pinged it up (injected methamphetamine into blood) for five years.
"I found it relatively easy to give it up but I smoked synnies for about a year and it was the hardest thing for me to give up. My body demanded it."
The family member said people might be angry with him for speaking out about his "brother's" use of synthetics.
"But I don't give a **** at the end of the day. He was my brother. That could happen to anyone."
The family member said what made him eventually give up the drug was that he vomited so much one day he thought he was going to die.
"It (giving up all drugs) has made me stronger and I just want to be there for people ... I want to put a stop to this (synthetics) s*** once and for all."
He described the use of synthetic cannabis as a really bad problem in the North Island and he was pleased he was now surrounded by good people and had a good job.
The family member said the dead man's immediate family were on their way to Rotorua from Australia and other areas for his funeral tomorrow. The Rotorua Daily Post spoke to the man's friends.
The friends, who didn't want to discuss the circumstances around the man's death, said he would always do something to make them laugh.
One friend said she felt like she had known him all her life, despite knowing him only a few months.
"He meant everything to us. We were always together."
She said the man had played a big part in their lives whether he knew it or not.
"We are going to be blessed with a big hole in our lives that is never going to be filled."
When they found out he had died, she said they "didn't want to believe it".
Another friend said the man was "an awesome guy".
"He's always there to help people when they need it."
He said their favourite pastime was hunting Pokemon, a gaming app.
"We were obsessed."
He said his friend of two years was always trying to make people laugh.
"I'll miss everything. Just him."
Several people have posted tributes to the man on his Facebook page, including one that said "Rest easy my bro ... gunna miss you man. Always going to remember the good times".
Last month at least 17 people were taken to Rotorua Hospital's emergency department to be treated after smoking the drug.
On August 12 a 44-year-old man was found dead at a Gifford Pl house. The man's death is also being referred to the coroner.
A Lakes District Health Board spokeswoman said a person was admitted to Rotorua Hospital's Emergency Department on Monday this week suffering from the effects of smoking synthetic cannabis. She said no one had been taken to hospital for at least a week before that.
Police and the Chief Coroner last week reinforced their warnings about the dangers of synthetic cannabis.
The Office of the Chief Coroner has about 20 cases under review where synthetic cannabis is a possible cause of death, up from 11 in July.
