LOS ANGELES A consultant to top state Democratic leaders has admitted that he molested two brothers while working at a Y-M-C-A more than 30 years ago. John Robert Stevens was an adviser to former Governor Gray Davis and Assembly speakers Antonio Villaraigosa (vee-yah-ry-GOH'-sah), Herb Wesson and Fabian Nunez. In April, he testified in a deposition for a lawsuit accusing the Y-M-C-A of Metropolitan Los Angeles of failing to protect the boys from Stevens' abuse. He admitted he fondled and masturbated the brothers, who were then 13 and 10, when he was youth director of the Rio Vista Y-M-C-A in South...