SINGAPORE - An 18-year-old youth, who repeatedly asked his younger sister to sexually stimulate him and promised to buy her merchandise featuring popular Korean pop group BTS in return, was sentenced on Wednesday (Jan 29) to 21 months' probation.

He must remain indoors from 10pm to 6am every day and perform 150 hours of community service.

His mother was also bonded for $5,000 to ensure his good behaviour.

The offender, who cannot be named owing to a court order to protect his sister's identity, pleaded guilty last December to asking his sister to perform an obscene act on him.

He also admitted to two counts of outraging her modesty in January and February last year.

The court heard on Wednesday that she is now living with her grandmother.

The 12-year-old girl had gone into her brother's room in January last year and sat on his bed.

She bolted from the room when he suddenly rubbed her private parts with his hand.

The family moved to another home soon after and the pair shared the same bedroom.

The teenager and his sister were in the living room in mid-February last year when they started arguing over what to watch on television.

Deputy Public Prosecutor Ryan Lim had earlier told District Judge Seah Chi-Ling: "The accused suddenly picked the victim up, carried the victim to their bedroom... and laid her on his bed.

"(The) accused used the fingers of his left hand to stroke the side of the victim's right breast over the victim's T-shirt in an upwards and downwards motion. The touching was non-fleeting."

The girl yelled at her brother to get out of the bedroom and he complied.

DPP Lim had said that on April 15 last year, the girl came home at around 6pm and found that the door to their bedroom was closed.

She knocked on the door and opened it after she received no response. The girl then saw her brother performing a sexual act.

She closed the door and went to the living room. He came out and repeatedly asked her to sexually stimulate him. He also promised to buy her merchandise featuring BTS in return.

She rejected his requests and made a police report nine days later.

For each count of molestation involving a victim below 14 years old, an offender can be jailed for up to five years and fined or caned.