He abuses his half brother and sister
They are half-siblings who share the same biological mother.
But this did not stop a man from sexually abusing his half-brother and half-sister in 2012 and 2013. The victims are now aged 14 and 11, respectively.
The man, now 25, was jailed for 7½ years on Monday.
Last month, he pleaded guilty to two counts of committing an indecent act on each half-sibling and one count of sexually penetrating the boy.
Six other charges - four counts of committing an indecent act on the boy and one count each of disorderly behaviour and voluntarily causing hurt - were taken into consideration during sentencing.
District Judge Shaiffudin Saruwan said that the accused was supposed to provide care and protection to his victims.
Stressing that the sexual exploitation was significant and persistent, the judge added: "Instead, he abused this position of trust by sexually exploiting them for his own perverse gratification.
"Because he was their older sibling, the victims had complied with his instructions without question."
The male victim had earlier been abused from December 2009 to January 2010 by his father's workplace helper, who was then living with them.
The helper, who is now 56, made the youngster perform oral sex on him on three occasions, and was jailed for six years last October.
Some time in 2012, the boy's half-brother took him to a multi-storey carpark near Tiong Bahru, where he made the boy, then 10, perform oral sex on him.
In June 2013, he sexually abused the boy again when they were at home.
That month, he also made his half-sister, then eight, perform a similar act.
By the time the parents found out about his offences soon after, his abuse of his half-brother had left such an impact that the boy also allegedly made his sister perform oral sex on him.
The boy has not been charged in court.