A family member of the victims also helped the duo in the offence, said police.
A man and his minor son allegedly raped nine-year-old twin sisters in Mailardevpally area in Hyderabad, police said on Thursday.
One Jaffar and his 16-year-old son, who are neighbours of the minor girls, allegedly raped them repeatedly over the past one year.
A family member of the victims also helped the duo in the offence, a police officer from Mailardevpally Police Station said, quoting from a complaint.
The sisters revealed about the alleged sexual assaults to a senior family member, who approached a city-based NGO working for child rights which in turn lodged a police complaint.
Based on the complaint, a case was registered under relevant sections of IPC and Prevention of Children from Sexual Offences Act, police said.
The police officer said they are investigating the matter, but no arrest has been made till now.
According to the NGO, the victims originally hail from Nepal and had settled in Hyderabad.
