Mick and Peter Watson were raised as Catholics and attended a Catholic secondary school in Ararat, Marian College.

"It was just a normal childhood out on the farm. We played sport, did all the usual things," Mick Watson told ABC Ballarat's Steve Martin.

That was until 1991, when a relatively young priest arrived at the school. He "wasn't a stereotypical priest", and a lot of the kids got on well with him. One of those who became friendly with Father Paul David Ryan was Peter.

Ryan invited Peter to spend the night at the parish house and it was there that he abused the 16-year-old. Almost overnight, Peter changed from a confident and popular student into "the complete opposite".

"He had no pride in himself, he lacked self-esteem."

Over the years, Peter turned to drugs and alcohol, and struggled to settle down.

"He'd get his life on track, he'd seem as though he was doing okay, then it would all fall in a heap and he'd be back to square one.

"It was a little bit of a mystery for a while, and then he confided in mum and dad. It answered a lot of questions about his behaviour."

Peter's parents were supportive and encouraged him to go to the police, but he said he couldn't.

In March 1999, Peter drove to Ballarat and admitted himself to a psychiatric ward. After being assessed, he left and didn't go back.

"And that was the last time he was seen."

That was until October that year when his body was found, after he took his own life.

But the torment for the Watson family didn't end there. Peter's body was buried in an unmarked grave and wasn't formally identified and returned to Ararat until six years later.

Since his death, Peter's parents have sought justice for their son. But the police said it would be difficult to prosecute the case since Peter was dead.

In 2006, Ryan was finally convicted of indecent assault for two other offences and spent a year behind bars. That same year, the Ballarat Bishop wrote Peter's parents a letter, apologising on behalf of the church.

During the Victorian Parliamentary Inquiry into clergy sexual abuse, Peter's mother, Helen, told her son's story.

Now that the Royal Commission into Institutional Responses to Child Sexual Abuse is underway, Mick wants other victims of Paul David Ryan to come forward. He wants justice for his brother and wants Ryan to admit to his brother's abuse.

"I think it would be naive to think there aren't more victims of this priest out there. It might really help some of these people get on with their lives.

"I know how hard it is, and I know what it does to a family and to an individual."

If you need support, you can call Lifeline on 13 11 14.

You can contact the Royal Commission via its website or call Crime Stoppers on 1800 333 000 if you have information.