Disha took to Twitter on Saturday to share her excitement over the project.
Shruti earlier opted out of Sangamithra due to “unavoidable circumstances”.
To be helmed by Sundar C. and produced by Sri Thenandal Films, the film will also be released in Telugu and Hindi.
The film, which will also star Jayam Ravi and Arya, will have music by A.R. Rahman.
Sangamithra will start shooting in December.