Faye and Ron Bishop's son Dean Browne was murdered three years ago by Nuku and Pandey-Johnson, who before the murder had set up his own shrine to serial killers.
The Bishops were unaware of the Facebook page until alerted to it by the Herald on Sunday. Ron Bishop said he was "amazed" Corrections had not moved to get the page shut down.
"I feel sorry for every other parent and family member who lost a living person," he said. "It's ghoulish. It's sick.
"Our son is in a dark void. He has no communication with anyone."
Portraits and biographies of inmates, like "prototypical psychopath" and rapist Paki Toia, adorn the "Parry Max K.O.B.K Mean-Breed NZ Hardcore Crimz" page. K.O.B.K is an abbreviation for "kill or be killed".
Paul Kuchenbecker's son Karl, a father-of-two, was gunned down near his Wainuiomata home in early 2007. Burton is in jail for the crime. Kuchenbecker said the public should remember why these men were locked up.
"The New Zealand public would be pretty horrified to see interaction in this way with serious criminals."
That it could happen showed how lax the New Zealand system was. "Go to China. Even go to the States. We're pretty relaxed about our jail sentences."
In 2004, Rotorua woman Coral Branch married convicted killer Scott Watson in jail. Their relationship began with letters. The marriage ended amicably three years later.
"Women who get into relationships with death row prisoners often have much in common with those who spend their lives creating shrines to and writing to celebrities," psychologist Dr Lorraine Sheridan told New Statesman last year.
The page advises admirers to pick one inmate and stick with him, "or you could end up getting someone chucked off the landing".
In an interview with the Herald on Sunday, a page administrator defended the site and said wardens were aware of it.
Nikki Tata said she helped start the page after talking to a friend locked up in C Block. She posts messages on behalf of the men.
Inmates were given little time for phone calls and needed contact, she said.
"From what I've been told, they appreciate the letters. It helps them stay connected to the outside world."
Tata played down concerns about risks to the safety of female penpals.
"These men are in prison for a long time," she said. "Some of these men won't be getting out. I've spoken with a few of the wardens. They said: 'Please write'."
The Corrections Department expressed outrage at the page, but would not say whether it would lay a complaint with Facebook.
"Its contents are inaccurate, spurious and misleading," a spokeswoman said.
"The public can be assured that prisoners do not have access to the internet.
"Maximum security is our highest form of security and prisoners housed here are considered to be an ongoing threat to staff, other prisoners and the community."
The Howard League for Penal Reform said domestic post was extremely slow to get to prisoners and they should be allowed internet usage, albeit in closely monitored settings.
"Obviously, you don't want them watching porn but really, I don't know what Corrections' reasoning would be (to withhold internet access)," spokeswoman Madeleine Rose said.
"They're allowed to watch TV and read books and newspapers."
Nikki Tata said her heart went out to victims, but added: "I hope they would have forgiveness in their heart and I hope they can move forward."
