The search was still on in the lake for the fourth day on Saturday as one more person who had boarded the boat was still missing, officials said.
The Government has suspended the steerman Victor and an assistant crew-member of the vessel which capsized in the lake in Thekkady on Wednesday after cruising five kilometres.
The rescuers first fished out the body of five-year old Aiswarya in the wee hours and that of her mother Senthil Kumari (36) later. The body of Aiswarya's father, Rakasekharan from Chennai, was recovered on Thursday.
The body of another girl, Apurva (14) from Hyderabad, was also pulled out from the lake and rescuers were now scouring for the body of her brother, District Collector Ashok Kumar Singh said.
A preliminary probe into Kerala's worst-ever boat tragedy in the Thekkady Lake located in the Periyar Wildlife Sanctuary had said that the sudden swerving of the vessel by the steerman was a possible reason for the mishap.
The Chief Inspector of Boats had said in his note that other factors like change in the speed of the double-decker boat or strong winds could have caused the vessel to turn. He had ruled out chances of the boat having any mechanical problem as it was launched only recently by the Kerala State Tourism Development Corporation.