Actor Nicholas Brendon, best known for his role as Xander Harris in the popular television series "Buffy the Vampire Slayer," has died, according to his family. He was 54.Brendon's family said in an Instagram post Friday night that he died "in his sleep of natural causes." "Most people know Nicky for his work as an actor and for the characters he brought to life over the years. In recent years Nicky has found his passion in painting and art," the family wrote in the post. "Nicky loved to share his enthusiastic talent with his family, friends and fans. He was passionate, sensitive, and endlessly driven to create." Actor Nicholas Brendon attends Wizard World Comic Con Philadelphia on June 2, 2017, in Philadelphia, Pennsylvania. Gilbert Carrasquillo / Getty Images Born in Los Angeles in 1971, Brendon originally wanted to become a professional baseball player, but pursued acting in his 20s to help manage his stutter.…