Daniel Atkins, 33, has been jailed for 15 years for rape and sexual assaults of children under 13 years old.
Atkins from Bridgend has been convicted on further counts of sexual assault by penetration and causing a child to engage in sexual activity.
His most recent offences were committed in 2022 but the investigation discovered that the abuse had been ongoing for the past six years.
Following a report to police, officers arrested Atkins on 7 May 2022 and he was charged and remanded the next day.
Detective Constable Leah Fox commented: “I want to pay tribute to the extreme bravery of the victims during the investigation. Their courage in reporting this sickening abuse to the police resulted in the conviction and lengthy sentence for Atkins.
“We also encourage any other complainants to come forward and report offences that may have been committed against them.
“Violence against women and girls is one of South Wales Police’s main priorities and this investigation highlights our commitment to securing convictions for such offences.”
Atkins was sentenced to 15 years imprisonment with an extended period on licence of 5 years.
He will also be a registered sex offender for life.