 He is the oldest of three siblings, has a younger sister Hana and younger brother David, who became a film director after his father.As a teenager, Sís developed an interest in Western culture, Allen Ginsberg's beat poetry, long hair for men, blue jeans and rock and roll, particularly the music of The Beatles, The Beach Boys and The Rolling Stones.Sís was educated at The High School of Applied Arts, the Academy of Applied Arts in Prague and the Royal College of Art in London, where he studied with Quentin Blake.