Both the incidents took place over the last two days and the accused duo have been arrested, they said.
The fathers -- Rahamatulla and Mangal Ahmed Nazir Shaikh--have been slapped charges under sections 376, 506 and 504 of the IPC and Protection of Children from Sexual Offence Act, 2012 sections 5(g),6 and 17, police said.
Rahamatulla, a resident of Kausa in Mumbra township lived with his second wife and step daughter.
It was since last year that he had been committing rape on the 14-year-old girl while they were alone, police said.
While Shaikh raped his nine-year-old stepdaughter repeatedly in their house in Nalla Sopara. He was arrested early today.