Thilakan, who featured in 300 films in his acting career, was in critical condition after suffering two heart attacks. He was 74.
"Malayalam great Thilakan sir is no more. Grew up watching his brilliant understated performances. Was supposed to do 'Ustad Hotel' with him," tweeted Siddharth.
"Ustad Hotel" was Thilakan's last film. Siddharth had to pull out as the male lead of the film due to his packed schedules.