Erattai Manithan

Erattai Manithan (Tamil: இரட்டை மனிதன்; English: "Double Person") is a 1982 Indian Tamil film, directed by K. Shankar and produced by S. Aadhilakshmi. The film stars S. S. Rajendran (who is also credited for film's script), Jaiganesh, Latha, Sumithra, Bhavani and V. K. Ramasamy in lead roles. The film had musical score by M. S. Viswanathan.
Plot.
Durai (S. S. Rajendran) is honest, straight-forward and lives by a strict moral code. His only family is his younger sister Vani (Sumithra) and he works as a manager for Thangavelu's (V. K. Ramasamy) company. Thangavelu's wife Mangalam (Manorama) and daughter Kannamma (Latha) constantly clash with Durai's stodgy attitude but Thangavelu appreciates him. Thangavelu's family watches a play and see Durai as an actor in it. Mangalam and Kannamma point out Durai's hypocrisy and duplicity in pursuing acting when he has such strict expectations of everyone else. When Thangavelu confronts him, Durai lies and invents a younger twin brother, Raja, that is an actor and singer. Thangavelu and his family fall for his act and hire Raja to be Kannamma's music teacher. In the meantime, Vani falls in love with Chandran (Jaiganesh), Durai's costar in his plays and also Thangavelu's nephew. Unknown to Vani, he's a cad that uses the ruse of producing films to get closer to various women. Kannamma falls in love with Raja who also loves her but is reticent due to his lies and her continuing dislike of Durai. Matters are further complicated when another of Durai's costars, Bhavani (Bhavani), learns the truth and blackmails him. Durai confesses all to Thangavelu's family and is forgiven but now has to face the ire of Chandran and Bhavani.
Soundtrack.
The soundtrack was composed by M. S. Viswanathan.