The fire broke out around 4 am in the stationery shop in which the victims used to live, Airoli fire station in-charge Eknath Pawar said.
On getting information about the blaze, firemen rushed to the spot. As the shop was locked from inside, they broke open the door to enter the premises engulfed with dense smoke, he said.
The shop owner, his brother and two toddlers, aged 1 and 2, were rescued from the premises, Pawar said.
The cause of the fire was being probed, he said, adding that preliminary findings indicated the blaze occurred due to a short-circuit.
The bodies have been sent to a government hospital for a postmortem examination, he added.
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