Jack has Anglo-Italian origins; his father, Guido, a maritime broker, left Genoa and moved to England to avoid retaliation after witnessing a robbery. In the mid-1970s, he participated in two films by Duccio Tessari: Zorro and La madama.

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His mother, Ingrid Hepner, is a former model of German, Jewish, and Polish descent, active in the London jet set of the 60s and 70s.

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His paternal grandfather, Dr. Giovanni Savoretti (after whom he is named), was one of the partisan signatories who participated in the liberation of Genoa from the Germans during World War II (a street in the municipality of Lavagna is dedicated to him, and in Genoa, a plaque bearing his name is located in Via XX Settembre).

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Jack was born in London but spent part of his adolescence in Carona (Lugano), where he attended TASIS (The American School in Switzerland), then moved to America and eventually settled back in England. Despite his guitar skills, he had never touched one until the age of 16. Neil McCormick of the Daily Telegraph described his voice as “rough, deep, and nostalgic.” He cites singer-songwriters such as Bob Dylan, Paul McCartney, Simon & Garfunkel, Serge Gainsbourg, Lucio Battisti, and Fabrizio De André as influences.