It's one of the most distressing crimes that exists, because of the suffering it inflicts on two innocents - both victim and perpetrator.
Child-on-child sexual abuse is becoming increasingly common around Australia, and it's thanks to the society we have all created, say the experts.
When we think about child rape, we typically think of twisted paedophiles who it is easy to despise. But hundreds of minors every year are being sexually assaulted by their peers, reports News.com.au.
Australian Childhood Foundation CEO Dr Joe Tucci, who runs one of just a few programs focused on sexualised behaviour in children, says the number of cases is only growing.
"The problem has been increasing over the past decade," he told news.com.au. "When we started running the program, we got about 10 referrals a year. Nowadays we'd get closer to 250."
Carolyn Worth, spokeswoman for Victoria's groundbreaking Centres Against Sexual Assault (CASA), says around 50 per cent of child victims have been abused by other children.
"It's usually an easily accessible child, cousins rather than strangers," she told news.com.au. "Children are nearly always abused by someone trusted or close to them.
"Paedophiles who go overseas and buy children are in some ways the minority, but they're the ones we see in the papers. Often, it's opportunistic - parents who don't have boundaries and are narcissistic - people abuse their own kids much more regularly.
That's also a shocking thing: 75 to 80 per cent of abusers are known to the children."
There are many causes for the abuse. Many of the children involved are growing up in "chaotic" families with no clear rules or unsupervised, unlimited access to the internet.
The experts agree pornography is a major risk factor.
"The advent of broadband has really changed the field," said Ms Worth. "Before, if kids wanted to look at something, they had to find their dad's Penthouse or Playboy. It isn't so since around 2006.
"There's actually very violent things floating around on free porn sites. From about 2010 or 2011, we were seeing children of 14 or 15 who had very strange ideas about relationships - anal sex and aggression. It's brought about a change we weren't quite ready for," she said.
"No one thought if you give a child an iPhone they're going to start taking pictures of their anatomy and sending it to people. We were playing catch-up. It's only recently it's become something that's really being looked at and researched."
Cassidy Trevan, 15, took her own life in 2015 after reporting that she had been gang-raped by boys at her school in Victoria.
In 2014, a mother told the ABC she had withdrawn her six-year-old son from an exclusive New South Wales primary school after her son was sexually abused by a classmate and told her boys were being forced to perform oral sex on other boys in the school toilets.
She said the headmaster dismissed her concerns. A similar situation emerged in Adelaide that same year.
Often, the children involved have themselves suffered abuse, or another kind of trauma, such as family violence or the loss of a significant relationship through separation or death.
Dr Tucci said the behaviour typically progressed from touching another child's genitalia to oral sex, intercourse, anal sex and penetration with objects. It is often accompanied by threats and intimidation.
"This behaviour doesn't come out of the blue," said Dr Tucci. "There's generally some stress in their life, sometimes direct sexual abuse kids have experienced from a family members or someone close to them. They seek ways of reducing the stress, sometimes by looking for intimacy.
"Their needs for love and care aren't met, so they don't know how to grow up in a way that they meet the need for love and care of others.
"They're disempowered. They look for dynamics where they can feel more powerful."
These often come from porn, he said, which offers "insidious messages about overcoming resistance."
While these children usually don't initially understand the impact of their aggression, they eventually learn there is some "reward", added Dr Tucci, and their behaviour worsens.
"We see kids of 16 or 17 who are engaged in very abusive behaviour - violence, threats, coercion, intimidation," he said. "They're very defensive, they deny it, they're ashamed, they don't want to talk about it. It isolates them from their family.
"There's a lot you have to work on with kids that have to change, but you can change them, especially if you tackle it early.
"They need intervention, treatment and changes in family behaviour."
That's often not happening, because shame and fear means abuse is so underreported, and children used to family violence have often been coerced into patterns of secrecy.
This week, Vice reported on Melbourne's Gatehouse Centre, which sees around 300 children a year who have abused other children. Gatehouse social worker Michael Keane told the publication these children were typically silent, restless or embarrassed.
"One of the hardest things is to get young people to acknowledge what they've done, and that it's wrong," he said.
Dr Gemma McKibbin from the University of Melbourne said the silence was worsened by grooming. "It takes an average of 25 years for someone to disclose child sexual abuse," she told Vice.
She said some perpetrators were recreating scenes they had watched, or trying to educate themselves about sex.
Up to 95 per cent of perpetrators are male, and two-thirds of victims female. When the perpetrators were girls, they had often suffered a "cocktail" of abuse and disadvantage, Dr McKibbin added.
Victoria sets the standard in Australia with around 14 centres for victims, who can be referred or self-referred, and the wait is still around eight weeks.
In other states and territories, which do not have such a system, it can be months before children get help. That's a long time if they are in danger in their own home.
Young perpetrators are therefore frequently removed from their homes for the protection of a young sibling.
"Often they're defined by the behaviour in the mind of the community, sometimes in the media, they're portrayed as sex fiends at just 10 or 11," said Dr Tucci. "They're young kids, some can't even tie their shoelaces.
"While they are responsible for what they've done, they're really not responsible for triggers that caused that behaviour in the first place - it's the adults who have abused them, exposed them to family violence and supported the porn industry."
• Lifeline: 0800 543 354 (available 24/7)
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• Youthline: 0800 376 633
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• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
If it is an emergency and you feel like you or someone else is at risk, call 111.
• Canterbury Support Line: 0800 777 846