Mrs. McNamara was born in Aviano, Italy; she came to the United States more than 40 years ago. Mrs. McNamara received a Liberal Arts & Science Program in Milan, Italy. As a teenager she showed horses and drove rally cars. She was married for more than three decades to Ernest Byfield, a former OSS officer and public relations executive. Mrs. McNamara has lived for many years on a farm in Middleburg, and is an avid tennis player.
Diana Masieri McNamara married Robert S. McNamara on September 16, 2004. They married in the Basilica of St. Francis in Assisi, Italy in a private ceremony.