Social workers have launched an investigation over claims Michael Jackson's youngest son was threatened with a stun-gun by one of his cousins. Officials opened a child protection file on the family after a 300,000-volt weapon was removed from the home where the late singer's three children live with their 80-year-old grandmother. Jackson's eight-year-old son Blanket was allegedly chased by his 13-year-old cousin Jaafar - the son of Michael's brother Jermaine - with the gun before being stopped by security guards.