Forty per cent of the members of the Brothers of St John of God had allegations of child sexual abuse made against them from 1950 until 2010, the Royal Commission into Institutional Responses to Child Sexual Abuse has revealed.

So who are the Brothers of St John of God?

The Catholic order first came to Australia in 1947, establishing a special school for boys with learning difficulties at Lake Macquarie in New South Wales.

They then opened schools at Cheltenham and Greensborough in Victoria, as well as a training farm at Lilydale.

Despite the similar name, the organisation is not linked to the Sisters of St John of God.

Dozens of boys at institutions run by the Brothers of St John of God have made allegations of abuse.

In 2002, the order admitted 24 boys and men with disabilities were abused in three homes in Victoria, and the order paid $3.6 million in compensation to the victims.

Bernard Barrett from the abuse victims' support group Broken Rites said he had spoken to dozens of victims of abuse within the order.

"They were providing services generally for disadvantaged people, orphans and other vulnerable people," he said.

"They were often residential institutions, and many of the victims there had no relatives to come and see them.

"And so, it was open season."

'Full extent of abuse not known, many victims remain silent'

Dr Barrett said he was not surprised by the proportion of brothers who had abuse allegations made against them.

"I wouldn't have been surprised if it was more than half of them," he said.

"Those figures given out today were purely the official complaints that have been recognised.

"Most victims of the Catholic Church remained silent, they don't go and ring the police, they remain silent until their lives break down.

"Many of them remained silent until the grave."

A former nun told the ABC's 7.30 program in 2012 of a culture of cover up within the Brothers of St John of God.

A spokesman for the order referred the ABC to the statement from Francis Sullivan, the head of the Catholic Church's Truth, Justice and Healing Council.

Senior Catholic leaders will continue giving evidence to the royal commission over the next three weeks.