A twelve-year-old boy acted out a sex scene from Grand Theft Auto - by raping his six-year-old sister, a court heard.
The boy raped his victim in the living room and a bedroom in their family home while adults were in another room or asleep, it was said.
He raped his six-year-old sister at their home in Wiltshire, on numerous occasions - including Christmas Day.
One incident began after the boy watched footage of a sexual act in a Grand Theft Auto video game with his victim, a court was told.
He then decided to recreate it with her while another younger sibling was still in the room.
His mother held his hand and looked close to tears as graphic details of the charges - three of rape and one of inciting the the girl to engage in sexual activity - were read out at Swindon Youth Court.
The youth who cannot be named for legal reasons was given a 12-month referral order. He pleaded guilty to all charges.
If he completes the order in the out-of-town therapeutic facility where he currently lives, the four charges will be removed from his criminal record.
The boy, now 13, sat impassively for most of the hearing.
But he smiled and chuckled when the judge talked to him about football - he hopes to play the sport professionally one day.
The judge also asked what he would do if he had the opportunity to commit his crimes again. The teen replied: 'I would stop myself, I have learned that it's wrong.'
Prosecutor Russell Pyne said: 'The victim confided in a school friend about what her brother made her do, which he called special bundles and snuggles.
'Her friend told a teacher, who said that the girl had seemed withdrawn and quiet up until then but became a lot happier after telling her about it.'
When interviewed by police, he initially denied the offences but later admitted his guilt.
Mr Pyne added: 'He had been watching sex acts in porn and wanted to see what it was like for himself.'
Gordon Hotson, defending, said: 'This is a one-off opportunity to help sort this young man out, give the youth offending team the chance to work with him and ensure that this never happens again.
'He's been opening up to staff and working well with them. There is no contact between him and his siblings, though they've expressed wishes to see him.'
His mother said: 'We just want to make things right and do what's best for the safety of the children.
'He's doing really well and I want to make sure we can all be a family again at some point.
'My daughter used to be very sad about it all because she worried this was her fault, but she's come on leaps and bounds, she's a very strong girl and there's not an ounce of sadness in her now, I'm so proud of her.'
He was added to the sex offenders register for two-and-a-half years.