Police suspect that the couple might have committed suicide but are uncertain about the cause of the child's death, officials said.
Police have identified the deceased as Jayesh Patel (35), his wife Bhumika (30) and son Naksh (4), who originally hail from Gujarat.
"Today morning, neighbours, who developed suspicion after the Patels did not open the door for long time, summoned the housing society office bearers and later called the police control room," said Senior Police Inspector (Chaturshringi) Dayanand Dhome.
"It is unclear how Naksh died and his post-mortem report is awaited," said the officer.
Police said friends and relatives of the Patels have informed that Naksh was unwell and Jayesh was worried about his son's health.
"We are in the process of recording the statements of the relatives," police added.