In 2013, an 11-year-old boy made his eight-year-old sister perform a sexual act on him.
He had been abused by his father's friend in that manner when he was seven. His own stepbrother did the same when he was 10.
When his father found out about the act and questioned him, he said his dad's 56-year-old friend and his stepbrother had abused him, and he had learnt it from them.
The boy, now 14, also revealed that there were several occasions when his stepbrother made him and his sister use their legs to rub his private parts.
Shocked, the father reported the matter to the police as well as the Ministry of Social and Family Development (MSF).
Yesterday, the 25-year-old stepbrother was convicted of sexual assault by penetration in a carpark in Havelock Road in 2012, and two counts of committing an indecent act on a child in 2013.
The 56-year-old friend, who had worked for the victim's father in his roti prata stall, has been jailed six years for his offences between December 2009 and January 2010.
None of the parties can be named due to a gag order.
Deputy Public Prosecutor Sruthi Boppana said investigations showed that some time in 2012, the stepbrother took the boy to a multi-storey carpark in Havelock Road, where he committed the offence at a staircase landing without the victim's consent.
The boy, then in Primary 4, kept the matter to himself as the accused told him not to tell anyone or else there would be a "big problem'' in the family.
On June 20, 2013, the boy was at home when his stepbrother came up to him, covered his mouth and took him to a room.
He made the boy lie down on the floor. The accused then did an obscene act before placing the boy's feet on his private parts to rub it.
During the same month, the accused asked his stepsister to go to a room and committed the same indecent act.
Defence lawyer G. Dinagaran said a doctor from the Institute of Mental Health had stated that the accused suffers from mild intellectual disability, and his social functioning is in the extremely low range.
His client, he said, was remorseful and deeply regretted his actions. Both his stepsiblings have forgiven him.
District Judge Shaiffudin Saruwan will sentence the accused on June 6.