The Royal Commission into Institutional Responses to Child Sexual Abuse has heard a devastating account of how a Catholic priest preyed on two generations of boys in the same family.

Tony Hersbach and his twin brother Will were molested by Father Victor Rubeo in Melbourne in the 1960s.

The priest then abused Tony's two sons, Paul and Adam, in the 1980s.

Paul Hersbach gave evidence to the commission on Monday, and he and his father gave an exclusive interview to the ABC's 7.30 program about how the domineering and charismatic priest managed to take hold and control their family.

"He was like a father, but like an incestuous father, so he had this real dark, secret side," Tony told 7.30.

"And you know, in our family life, he was able to do whatever he wanted to. He basically took over."

Paul said: "We called him Grandpa, which... bothers me a lot.

"And he was just there ... he involved himself, uninvited, and he took over.

"He preyed upon my father. And our family. And no-one asked him. So we never did anything to keep him in our life."

The Hersbach family immigrated to Melbourne in 1955 when Tony, now 61, was two years old.

The family were poor and lived in a housing commission home in working class Altona.

Father Rubeo lived across the road.

"He came around trying to recruit altar boys," Tony said.

"And I put my hand up and said yeah, I'd be an altar boy. I was about nine, 10 years old."

Tony and his twin brother Will served as altar boys for several years.

Father Rubeo would ply the boys with gifts and help them with their homework, but soon the attention became more sinister.

"He would have these rituals almost where he would make me dinner as if he was taking me out on a date," Tony said.

"I even remember him taking me to really fancy restaurants.He would take me there sometimes on a Saturday night. [We would] have this marvellous dinner - just he and I together.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 9 minutes 12 seconds 9 m Two generations abused by same priest

"And then he would bring me home and he would ... he'd basically have sex.

"It was always premeditated. It always involved him plying me with lots of alcohol. We'd have shots of Drambuie, fine wine, all the rest of it.

"It's not just the actual sexual abuse, it's all of the grooming and the way that it's done.

"I hated it. I hated it. I hated every minute of it. But I never said anything or could do anything because he had this ... such a hold over me."

Tony's father was an aggressive alcoholic, and the priest took over the father role.

"I was someone who needed a father ... and I wish I could've told him all that time ago to leave me alone," Tony said.

Priest began abusing Tony's children

But Father Rubeo did not leave Tony or his family alone.

The priest bought Tony his first car, and when Tony married his wife Lou, Father Rubeo put a deposit into their bank account for their first home.

"And it would just turn up, unannounced, stuff you didn't want, you didn't ask for, it just happened," Tony said.

The abuse remained his darkest secret. He never told his twin brother, he never told his wife.

And all the while, Father Rubeo was everywhere – family holidays, christenings, and birthdays.

"He used to take all sorts of liberties. He would open our mail. He would sometimes walk in unannounced to our bedroom," Tony said.

Tony's wife Lou says the priest often babysat their children.

Will and Tony Hersbach (photographed here in the 1960s) were both abused by Father Rubeo. ( Supplied )

"He had full care of them, from bathing them to changing their nappies, to dressing them, the taking them to school, to picking them up, to taking them on outings," Mrs Hersbach said.

"He was with us on holidays - he was like their surrogate grandfather."

The family even stayed for a time in the presbytery of the church where Father Rubeo was parish priest.

That is where Father Rubeo started on the next generation of Hersbachs – turning his attention to Paul Hersbach and his older brother Adam.

"He would invite himself into my bedroom and my brother's bedroom," Paul told 7.30.

"He would come into the bathroom - while we were in there, bathing.

"He would also invite us and allow us to come into his bathroom when he was either showering or shaving. And times then I'd see him masturbate."

Tony feels terrible about this now.

"The acknowledgement of the fact that as a father, I didn't protect my children. And that's something that I have to take responsibility for," he said.

"There was a lot of reasons for that.

"He did have enormous control over me because of what he did to me."

By the early 1990s and in his 40s, Tony had a breakdown and finally admitted to his wife what had happened.

He also told the Church about Father Rubeo's crimes.

"I remember the date very clearly. Lou and I went together to see Vicar General Cudmore. It was the 10th of August 1994," Tony said.

Father Rubeo was then parish priest at St Joseph's Boronia in Melbourne's outer east – a church with a school attached and attended by young families.

Years later, after getting access to Vicar General Cudmore's notes, Tony discovered that the Church did nothing.

"Cudmore made some notes which showed that he [Father Rubeo] offered to resign and it wasn't accepted," Tony said.

"He was left in his parish for a further two years."

Tony learned brother Will was also a victim of Rubeo

In 1996, the police contacted Tony and his brother Will to tell them Father Rubeo had confessed to abusing them.

That was when Tony learned that for all those years earlier, his brother had also been a victim.

Neither twin had told the other.

"He was charged with two counts of indecent assault - one against my brother and one against me. And he was given a good behaviour bond. With no conviction," Tony said.

In 2004, Tony's son dropped a bombshell. Paul admitted he too was a victim of Father Rubeo.

His parents were devastated.

"[I felt] immense guilt. Immense shame. Great regret," Mrs Hersbach said.

"I felt inadequate as a mum.

"I can't begin to re-step those years and change things and I wish I could.

"I know a lot has been taken from the kids, not just through Paul's abuse and Tony's abuse, but through the way the man was in our life.

"I know our family was good, it was good, but it could have been so, so much better."

In 2010, the Hersbach family again went to the police and Father Rubeo was charged with a further 30 offences.

He died the day he was due to face court.

The Hersbachs are now rebuilding their lives.

Their family photo album is littered with gaps where the photos of Father Rubeo have been taken out and burned.

Royal commission hears evidence about Melbourne Response

Paul gave evidence to the child sex abuse royal commission on Monday, where he outlined the inadequacy of the Catholic Church's Melbourne Response.

When he was interviewed by the Catholic Church's independent commissioner, Peter O'Callaghan, about Father Rubeo's abuse, he says Mr O'Callaghan told him it was unlikely the police would press charges because his case was too weak.

Both Paul and Tony, once dedicated Catholics, have lost their faith.

Paul says he does not blame his father Tony for the abuse he suffered. ( Supplied )

Now they want the Church to be called to account.

"Society has stepped in and said 'this is not OK, we want to do something about it'," Paul said.

"And what I want to come from it, apart from the Catholic Church having to redress what wrongs they've done, is for people, victims - any type of victims - to understand that you can break the cycle."

As for his relationship with his father, Paul holds absolutely no malice and does not blame him for the abuse he suffered.

He knows what it is like to be a victim of Father Rubeo and why the priest had such a powerful hold on Tony.

"I'm very proud of him for what he did," Paul said.

"To come out after 30 or 40 years takes an immense amount of courage - for anyone to come out in these circumstances takes an immense amount of courage.

"The crimes were committed by Rubeo. Not my father."