They are children of a self-styled religious teacher who has 10 wives and 65 children.
The court heard on Wednesday that Ahmad Habiibul Hakim Assalafi, 19, had introduced his sister, Nuurul Aliyyah Abdul Talib, 23, to an alleged pimp and she agreed to work as a prostitute.
He pleaded guilty to six charges, including two counts of abetting commercial sex with another prostitute who is underage and one count of voluntarily causing grievous hurt.
Nine other charges for similar offences will be taken into consideration during sentencing.
He has been absent without official leave from National Service since January and did not return to his flat in Marsiling, the court heard.
At around the same time, he befriended the prostitute, then 16, on Facebook and they became a couple by early February.
Deputy Public Prosecutor (DPP) Stella Tan said the girl introduced him to alleged pimp Malcolm Graham Head, 32, and his girlfriend, Veronica Patricia Rio, 18, later that month.
When Head agreed to let Ahmad become his assistant, the latter roped in Nuurul Aliyyah to work for Head. Between Feb 22 and March 4, Ahmad accompanied Head in escorting his girlfriend, the teen prostitute, to meet her customers, who paid between $180 and $350 per booking, DPP Tan said.
ANAL SEX REQUEST
But things went awry on March 4 when a customer asked for anal sex from his sister.
Ahmad, Head, Rio, Nuurul Aliyyah and her friend, Nur Azilah Ithnin, 20, ganged up against French expatriate Didier Moise Dominguez, 53. The product line manager suffered a broken jaw and a black eye, among other injuries.
District Judge Hamidah Ibrahim has called for pre-sentence and reformative training centre reports to determine a suitable sentence for Ahmad. He will be back in court on Oct 22.
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