Kalaba Kadhalan (2006)

A young man marries and the couple are content, until his wife's younger sister comes to stay with them. She becomes infatuated with her brother-in-law, and her obsession grows into a menacing campaign to separate him from his wife. Kalaba Kadhalan is an early lead film for Arya, before Naan Kadavul and Madrasapattinam made him a star, with Renuka Menon as the wife and Akshaya as the obsessed sister. It is a domestic thriller that turns family closeness into suspense.