The nephew, who wished to remain anonymous, said the first the family heard of the accusations was in the media.
"I am absolutely shocked and feel betrayed. My mother doted on him. He was just another uncle," he said.
"It is one skeleton I didn't expect to come out of the closet."
The nephew said he was glad his own mother had died not knowing what Shirres had done. Shirres' brother, John, had also died about five years ago.
"I don't believe his own brother had any idea of what his brother had done," he said.
He said the only thing that gave weight to the new accusations was that Shirres became a recluse later in life.
"I was given some of Uncle Paul's memorabilia by one of his fellow lecturers only last year, which I was chuffed to have, but I am not feeling so chuffed now," he said.
A University of Auckland spokeswoman said staff who had known Shirres were also shocked to learn of his past.
"To the best of our knowledge there is no record of knowledge of this at the university or complaints made to the university," she said.
Among Shirres' victims was Annie Hill, 56, a former art teacher at Pompallier College in Whangarei, who received a written apology from the priest for sexually abusing her.
Hill left her job in 1995 after suffering severe panic attacks brought on when she discovered Shirres had been invited to talk at the school. She was later diagnosed with post-traumatic stress disorder, the result of sexual abuse by the Dominican priest beginning when she was 5.
Hill said she had been haunted by the knowledge she was not the only victim and that many vulnerable Māori children may have suffered a similar fate, given Shirres' unique access to those communities.
Hill said she believed it was known within church circles as early as 1966 that Shirres was an active child abuser when he returned to Auckland.
Shirres was eventually withdrawn from pastoral ministry in late 1993 and entered into the Safe Network programme to address his predatory behaviour.
However, he continued lecturing at the Catholic Institute of Theology and the University of Auckland until May 1994, when he was demoted from priest to religious brother.
The Catholic Bishop for the Auckland Diocese, Pat Dunn, told the Herald that the church had received five complaints in 1993 relating to Shirres' sexual abusing.
However another of Shirres' victims, Auckland woman Marcelle Kiely, said a therapist who had treated her and had coincidentally also worked with Shirres at Safe told her the priest had admitted to dozens of victims.
Kiely, 61, said the therapist, known to the Herald, confided to her in 1994 that Shirres had been requested to unstack chairs, each one to symbolise a victim he must apologise to, during a role play. The priest reportedly lined out "several rows of chairs" across the room.
Shirres' nephew said he was wary of the factuality of these statements.
"As a Catholic Priest he is seen to be guilty even if he just had those thoughts," he said.
"He was obliged to admit those thoughts, so the number may not have been as high as he actually made out himself, but in his mind it was."
Dunn said the church had acted appropriately when complaints were made.
"My understanding is that the Dominican Order certainly worked with the complainants after Michael Shirres admitted the abuse," he said.
"I am confident that the Dominican Order would have scrupulously followed whatever advice was given by the Safe Network in 1993."
Do you need help?
If you've ever experienced sexual assault or abuse and need to talk to someone call the confidential crisis helpline on: 0800 227 233 (08002B SAFE).
If it's an emergency and you feel that you or someone else is at risk, call 111.
