Willem Bowen Scheeren abused his nephew, Antony Vote, when Mr Vote was a young boy in Canberra during the late 1980s.

The abuse had such an impact on Mr Vote, 39, he still finds it difficult to meet people without thinking about what happened.

And Mr Vote's mother, Robin, has laid bare her "greatest guilt" and despair, blaming herself for not protecting her son from her brother.

At a hearing in the ACT Supreme Court on Wednesday, Mr Vote and his mother addressed the court, detailing the impact Scheeren's abuse had on them as he sat before them.

Ms Vote, composed as she read from the witness stand, said she looked back with shame at "my carelessness and naivety".

"It's a terrible story, which perhaps explains why I have become a very sad and strange person ... I trust no one except my children."

She said her brother had taken a "particular interest" in her son; they went camping and fishing on the weekends and holidays.

Ms Vote said she was grateful and happy for the companionship Scheeren gave her son, and the activities to keep him safe.

But she said Mr Vote's behaviour later deteriorated at both school and home, and he was expelled from his Sydney school.

It was only years later, after Mr Vote had become addicted to heroin and spent time in rehab, that he revealed the abuse he suffered.

Ms Vote said at the time some members of her family were unable to offer much support.

"My mother told me she partially blamed Antony ... she also told me that she had known for a long time that Willem was probably a paedophile, but that she never imagined he would do anything to a family member," Ms Vote said.

She said Scheeren told her the abuse was his way of showing love.

Mr Vote, equally brave and composed as he read from the stand, said the abuse by his uncle had shattered the once close-knit family.

"The impact it has had on my mother is what affects me the most. She had a close relationship with her family, especially her mother."

He spoke of his self-blame and confusion about his sexuality.

He battled drug addiction, and found it difficult to have relationships, pursue a career, or spend quality time with his nieces and nephews.

"I'm always feeling uncomfortable with thoughts of them thinking I could be the same as my uncle. I get paranoid when I take them to the park or somewhere alone that my sisters are thinking that I could possibly abuse them."

But Ms Vote still hoped for her son's future, crying as she spoke.

"Antony is a loving and beloved son and brother. He has suffered enormously and of course I share his pain. To observe my handsome and highly intelligent child living with no joy or achievements in his life has been drawn-out torture for me.

"He is now turning a corner and is recovering from his past."

The prisoner Scheeren is expected to be sentenced early next month.