The accused had threatened the girl with dire consequences if she told anyone about the matter and raped her several times over the past four to five months, police said.
The girl's mother, also the wife of the accused, registered a complaint with the police, following which he was arrested yesterday, they said.
The victim's mother had married the accused after her first marriage had broken up. She had two daughters from her first husband, police said.
The matter is being probed, they said.