Rob Reiner, the son of a comedy giant who went on to become one, himself, as one of the preeminent filmmakers of his generation with movies such as “The Princess Bride,” “When Harry Met Sally …” and “This Is Spinal Tap,” has died. He was 78. Reiner and his wife, Michele Singer, were found dead Sunday at their Brentwood home. Authorities were investigating it as an “apparent homicide.” Reiner rose to fame through the role of Meathead on the TV series “All in the Family,” which won him two Emmy Awards. Between 1986 and 1989, he directed a trio of American classics, all of them among the most often quoted movies of the 20th century.