A longtime mystery about Marilyn Monroe may have been solved. A new documentary, “Marilyn: Her Final Secret,” claims that the sex symbol’s sire is a man named Charles Stanley Gifford. Gifford had a brief affair with Marilyn’s mother, Gladys, in 1925. Marilyn claimed he was her dad, but Gifford denied it. To test the hypothesis, experts used a strand of Marilyn’s hair, taken shortly after she died. They matched it with a saliva sample from one of Gifford’s descendants.