All that jazz is all in the family With guidance from father, a young vocalist finds niche By Robert Knox, Globe Correspondent | November 2, 2006 Leah Souza of Plymouth is saluted by critics as one of the "freshest faces in contemporary jazz" and already, at age 24, is recognized as a "superb" jazz vocalist. How did she become so successful so young? "Blessed with good ears," she says. Souza grew up in a musical family. She recalls the day her father, l …