Damien: Omen II (1978)

Richard (William Holden) and Ann Thorn (Lee Grant) have taken their 13-year-old nephew, Damien (Jonathan Scott-Taylor), into their Chicago home following the death of Richard's brother seven years earlier. The Thorns love the child, whom they are sending to military school, but not everyone is so sanguine about his presence. Soon after Great Aunt Marion (Sylvia Sidney) expresses concerns about the boy, she dies suddenly and unexpectedly. And she is certainly not the last.