He asked his father whether he had done what he was accused of.
"He didn't answer me right away. I asked him again because his reaction seemed strange to me," he said.
"When someone's innocent or something they'd say 'I didn't do this, these allegations are horrible, you've got to believe me, I didn't do this'. There was nothing like that. He just jumped right to 'I got a lawyer'."
The son persisted with the question, despite his father telling him several times his lawyer had instructed him not to go into details of the charges.
"Finally he said yes. In a soft voice again, he said yes."
The son said he became upset, and at times shouted down the phone at his father.
"Hearing something from your own parent like that . . . I was shocked, my head filled with questions. Part of my thinking went to I was worried that perhaps myself and even my brother was assaulted when we were younger and we just didn't remember it."
He said Raymond Bradley assured him he had never offended against him and his brother.
You're guilty and you need to pay the price for it, whatever that is.
"I was pretty emotional, as you can imagine."
The son eventually became so emotional that he ended the call.
He said Raymond Bradley later sent an email to he and his brother, saying he was "at peace" with the charges and was going to fight them in court.
"For some strange reason in his mind he had come to terms with this."
Kristen Bradley asked his father how he could put the two complainants through a court trial "when you full well admitted you did this".
"You're guilty and you need to pay the price for it, whatever that is."
Defence lawyer Wayne McKean said Raymond Bradley's evidence was that his son began "offloading" during the phone call they had.
He asked whether Kristen Bradley said to his father that he had abandoned him and his brother when separating from their mother.
He agreed, saying the revelations about the sexual charges would have brought many emotions to the fore.
McKean asked whether the son realised that during a long pause in between asking whether his father had committed the crimes, and getting an answer, Raymond Bradley was actually speaking to somebody else on the other end of the phone.
The son said he did not know that.
Raymond Bradley is said to have offended against both girls on a number of occasions between 1960 and 1972. The earliest charge is dated between 1960 and 1961, when the complainant was about 7 or 8 years old, and Bradley would have been 13 or 14.
He faces five counts of rape, three of indecent assault, three of performing an indecent act, and one of inducing a girl to do an indecent act on him.
Bradley moved to the US when he was a young man and lived there permanently until a few years ago when he moved back to New Zealand.
Upon finding out he was living in New Zealand again, the complainants contacted police about the historic allegations.