The victim's grandmother -- the accused's daughter -- was also arrested for trying to destroy evidence, police said.
Both the accused (names not disclosed) have been booked under the Protection of Children from Sexual Offences Act and remanded in police custody till August 20.
According to the police, the victim had gone to the accused's house for a short stay, when she was sexually abused on the night of August 15 when others were asleep.
The girl's mother noted next day that she was bleeding and took her to a hospital, where doctors said it was a case of sexual assault.
During initial interrogation, the accused allegedly told the police that his daughter -- the victim's grandmother -- learnt about the incident and she washed the child's clothes to remove blood stains.
"We have arrested her too," said a police officer.
Police are further probing if the accused had sexually abused the victim or any other girl in the past.
