Dolly Parton is notoriously private when it comes to her personal life but over the years has given insights into the secret behind her decades-long marriage.MORE: Dolly Parton and Kelsea Ballerini's fans all notice the same things from their ACM performanceThe country superstar has been married to Carl Dean since 1966 and recently put one of the many reasons it's a success down to their star signs."We are good friends, we respect each other. We like each other.