SINGAPORE - A 16-year-old boy pleaded guilty on Monday (June 4) to sexually penetrating and molesting his younger sister when she was just 10 and he, 12.

The offences took place over a span of three years, from 2013 to 2016. The boy's mother reported him to the police in April last year.

The polytechnic student faced two charges, one each for sexually penetrating without consent and molesting his sister, who is now 15. Six other charges of similar nature will be taken into consideration during his sentencing. The biological siblings cannot be named due to a gag order to protect the girl's identity.

The court heard that some time in 2013, when the boy was 12, he chanced upon pornography while surfing the Net. Initially disgusted, he grew interested in it and began surfing pornography websites, sexually stimulating himself regularly. He eventually wanted to try what he saw on these sites.

In September 2013, he was home alone with his sister when he became aroused after seeing a sex scene on television. He called his sister, then 10, into his bedroom and told her he wanted to try something with her. He threatened her, telling her that he would report her mobile phone usage to their parents if she did not comply.

He then told her to strip and proceeded to touch her genitals and penetrate her. When his sister complained of pain, he stopped and asked her to leave the room and sexually stimulated himself.

He repeated the same offences against her several times until March 2014. When his offences were discovered by his parents, the siblings were given counselling and the boy was sent to live with his grandparents. After six months, he was allowed to return home and house rules were implemented to prevent a recurrence.

But, in August 2016, the boy started watching pornography again and, on one night, he felt a strong sexual urge. He asked his sister to follow him to his bedroom, then touched her breasts and genitals under her clothes.

When his mother found out about the recurrence, the matter was reported and referred to the Ministry of Social and Family Development (MSF). The police were alerted.

Deputy Public Prosecutor Raja Mohan said that the boy committed the offences against his sister as she was in close proximity to him, and also because he was confident that she would not disclose to others what he did to her.

The siblings now live apart and the boy is currently seeing a psychologist from MSF and a psychiatrist from the National University Hospital regularly. He is not on any medication.

In court, the boy kept his head down as his acts were read out. When District Judge May Mesenas asked if he had anything to say, he replied: "It was very wrong of me, I would like to apologise to my sister."

The boy's parents also appeared in court and his mother cried as she pleaded for leniency from Judge Mesenas. She added that her daughter was attending counselling regularly.

Addressing the boy directly, Judge Mesenas said: "I can't imagine what your sister had to go through. The effects from your actions are very permanent and it would take a long time for her to heal."

The court was adjourned to assess the boy's suitability for probation and he is due to appear in court again on July 9. He is expected to be sentenced then.

He faces up to 20 years in jail, with a fine or caning, for penetrating a girl under 16.