Mumbai: Film producer Smita Thackeray said that the cast of the biopic on her late father-in-law, Shiv Sena founder Balasaheb Thackeray, to be directed by her son Rahul, is almost finalized but they want to keep the "mystery" alive. "As the script develops, we will cast who we feel can play the characters; we will give those actors the chance who we feel can play the really good characters. I wouldn't like to reveal if we'll cast freshers or established actors, but most of our casting has been completed and the main actors, we have kept them on hold till the script is completed," said Smita. Rahul said: "We want to keep the mystery alive. When this project will be fully ready, that time we will reveal properly about the artists." It was in August last year that the biopic on Thackeray was announced. "Mary Kom" director Omung Kumar and Sandeep Singh, who recently produced "Sarbjit" together, are also producers of the film along with Smita and Rashid Saeed. "The journey till now have been very exciting. I met numerous politicians who were close to him (Thackeray), who had worked with him, about what they learned from him. I spoke to a lot of Shiv Sainiks who have, from the beginning, seen the journey of Shiv Sena. I spoke to all the family members who have a lot of memories that my grandfather shared with us, when we would sit and talk. I am still researching, still learning," Rahul said. Does Smita give her inputs to Rahul while scripting? "He did the whole R&D. But in a week at least 1-2 times the writer, Rahul and me sit and brainstorm on our progress and suggestions," she said. "I had this wish since many years of making a film on my grandfather. And I am on way to fulfill the dream. It will be film close to his heart, the way we have loved him, that is what I want to show," Rahul said. Rahul said that the film will primarily be in Hindi and they are looking for release next year.