The 37-year-old man was convicted and sentenced for two counts of rape and two counts of sexual assault, said Captain Thulani Zwane.
He was sentenced to 10 years imprisonment for each count of rape and five years for each count of sexual assault.
The man was found guilty of raping his step-daughter and another girl, both aged 13.
He was also found guilty of sexually assaulting two other girls, aged between six and eight, who visited his step-daughter between 2008 and 2011.
“He would call the victims to visit his residence in New Germany and he would take them to a swimming pool where he repeatedly raped them,” said Zwane.
The rape and sexual assault cases were reported to the Pinetown police station and the man was arrested when the cases were handed over to the Pinetown family violence, child protection, and sexual offences unit.