The family, which stays in Greenhills Colony in the city's Chaitanyapuri area, brought the girl six months ago from Suryapet, around 140 km away. Less than 16, she is reportedly pregnant.
Sudhakar Reddy, 60, and his 30-year-old son Bharat Kumar Reddy, both lawyers, have been arrested.
Cases of crime against children, rape and sexual assault and bonded labour have been filed against them.
Sudhakar Reddy's wife and daughter also live with him.
When the help complained about assault some months ago, she was allegedly beaten. She had no access to any phone.