The bodies of Vasanthi (53) and Abu Sri (12) were found among bushes in the compound of their house late last night, they said.
Police said the customs employee Subbaiah was missing and suspect he might have been kidnapped.
They said Subbaiah's cell phone was found switched off. Enquiries with his brother revealed that he had spoken to him.
Subbiah had recently made out a will, apportioning equal share of his property to his adopted daughter and his niece.