The real name of Dipper Pines is Thomas Desman. He is actually a son of Mabel from the future and he came into 2012 to destroy Bill and save the universe. Desman's body was turned to body of real Mabel's twin who died before trip to Gravity Falls, and his memories were changed too. In 2012, only Bill Cipher and young version of Mabel know about Dipper's real identity and only Mabel can unblock it (that's why she was captured by Bill).
