Lakshmanan the youngest of the three sibblings allegedly hacked his sister Suseela and his brother Raman after a heated exchange and scuffling. He also threw a boulder on the head of his brother.
While Suseela died on the spot, Raman, who was rushed to the Government Rajaji Hospital here, died on the way.
Vikramangalam police registered a case and arrested Lakshmanan who was hiding in a nearby village.