Beyonce Knowles believes the key to her relationship with Jay-Z is their friendship.The couple were friends for over a year before they started dating and Beyonce, 31, thinks their friendship is one of the key factors in their strong marriage.She told chat show host Oprah Winfrey: "We were friends first for a year and a half before we went on any dates. We were on the phone for a year and a half, and that foundation is so important for a relationship. Just to have someone who you just like is so important, and someone [who] is honest."Â Beyonce also praises Jay-Z, 43, the father of her 13-month-old daughter Blue Ivy, as a huge part of her success.She said: "I would not be the woman I am if I did not go home to that man. It just gives me such a foundation. [He's helped me] on so many levels."Â While the couple love being parents to Blue Ivy, they suffered heartbreak when Beyonce's first pregnancy ended in miscarriage, which was first revealed in her husband's song 'Glory'.She previously explained: "[The miscarriage] was the saddest thing I've ever been through. My life is a journey ... I had to go through my miscarriage, I believe I had to go through owning my company and managing myself.Â "Ultimately your independence comes from knowing who you are and you being happy with yourself."