Dispute between husband and wife was suspected to be the reason behind the act, Police Inspector Manoharan said.
Kannan (27) and Pandeeswari (25) were married few years ago but were living separately following some differences for the last one year.
Few days ago, some villagers attempted to reunite the couple and asked Kannan, who was staying in Chennai, to return to the village.
Pandeeswari, it is alleged, came to the house where Kannan was staying, locked it from outside and set it on fire after pouring kerosene. She later surrendered before the Sadapetti Police, he said, adding investigations were on.
Kannan, his parents Velu (65) and Pachiammal (50), Kannan's sister Sugandhi (35), her children Sangeetha (17) and Sangeeth (12) died of burns in the house.
Vineeth (13), who was rushed to Madurai Government hospital by neighbours, succumbed to burn injuries, police said.