David Foster and Katharine McPhee have a marriage without hard and fast rules

David Foster, 73, opens up about marriage to Katharine McPhee, 39. The famed music producer, 74, spoke about his relationship with the singer, 39, in a new interview. Foster: "For David Foster and Katharine McPhee marriage is about compromise"

David Foster and Katharine McPhee have a marriage without 'hard and fast rules' David Foster revealed why a marriage is not hard and fast. The couple have a three-year-old daughter, Rennie, 3, and have a son together. The producer revealed why they have a relationship without hard or fast rules.