The woman Kavitha had set herself and her two chidren, Harikrishnan (5) and Saradeshan (11) on fire, while the husband, Saravanan was away in Tirupur.
The incident took place early in the morning when the neighbours, on noticing heavy smoke emanating from the house, broke opened the door and entered it only to find the burnt bodies of Kavitha and her son Saradeshan.
However, Harikrishnan was rescued and admitted to Madurai Government Rajaji Hospital where he died without responding to the medical treatment today.
Reason for the suicide of the woman is not known, police said.
Further investigations are on.