Complex sentence: He also coached a number of actors in the art of professional singing (Kristy McNichol, Scott Baio, Phillip McKeon and others) in his own career, which began at the age of 15 when he was given his own radio show in San Francisco.
Split into simpler sentences: He also coached a number of actors in the art of professional singing, these include Kristy McNichol, Scott Baio and Phillip McKeon, during his career. His career began at the age of 15 when he was given his own radio show in San Francisco.