Fede Alvarez included a youthful cast in ‘Alien: Romulus’ to create extra terror for the audience. The 46-year-old director has helmed the new movie in the sci-fi horror franchise and thinks the presence of fledgling stars such as Cailee Spaeny and Isabela Merced will resonate deeply with viewers. Fede told Variety about his decision to include a young cast: “For me it was a way in to imagine what it would be to a bunch of young people, to grow in one of these colonies in sci-fi and at the end of the world and having to face this creature. They’re closer to the audience in a way. They don’t kn…