A teenage boy who raped his younger sister numerous times claims he later found out the conduct was "not only messed up but a criminal offence".
"This isn't normal," the victim said while verbally resisting her brother on the first occasion.
He responded: "Other people do it and it's normal. No one will find out and it's fine."
The case returned to the ACT Supreme Court after the teenager, who cannot be named, previously admitted to a single charge of incest.
On Thursday, he received a two-year supervised good behaviour order after Acting Justice Rebecca Christensen described the teenager's and the victim's parents as heartbroken.
"This is a complex, difficult and traumatic case," the judge said while delivering a sentence she described as giving considerable weight to rehabilitation.
Acting Justice Christensen read a redacted version of the victim's impact statement, in an effort to give her a voice "lost by the criminal justice response".
"I feel like what I wanted hasn't mattered in this process," the victim wrote.
The child detailed how she never wanted her brother charged but had been assured by the counsellor she disclosed the allegations to she could speak to police without the case necessarily progressing.
"All I want now is for this to be over so we can move forward. I just want my family back," she wrote.
"I want [the young person] to get help and have a good life."
The judge said there had been about 10 occasions of sexual intercourse over a more than two-year period, starting when the victim was aged 11 and her brother was 14 years old.
The sexual assaults took place mostly at the family home.
Acting Justice Christensen found the young girl never initiated or encouraged the criminal conduct and was directed by her brother.
In a letter to the court, he apologised for the pain he had put his family through.
"A big brother is supposed to be someone their younger siblings can rely on to always look after them and protect them," he wrote.
"I have failed as an older brother."
The judge found the teenager had expressed genuine remorse for his actions, but she held reservations about his insight into the crimes after he claimed there had been "mutual curiosity" in the beginning.
The boy made full admissions to police.
Acting Justice Christensen also ordered the offender not be placed on the child sex offenders register, which includes onerous reporting conditions for several years.
She accepted a defence application not to do so due to the teenager's "excellent prospects" of rehabilitation, a psychologist's recommendation, and the victim's and family's wishes.
"I can give voice to the victim in this regard," the judge said.
Acting Justice Christensen asked the teenager, who held his face in his hands throughout sentencing proceedings, if he had any questions about the conditions of his good behaviour order.
"No, your honour," he responded.
He has previously spent one night in custody for his crime.
- Support is available for those who may be distressed. Phone Lifeline 13 11 14; MensLine 1300 789 978; Kids Helpline 1800 551 800; Canberra Rape Crisis Centre 6247 2525; Bravehearts 1800 272 831; Blue Knot Foundation 1300 657 380.
