Born in Milwaukee, she attended Smith College, where she received a bachelor's degree in English. While on a ski trip to Sun Valley, Idaho, she met the man who would become her first husband, Robert Adam Bradford of Boston. They married in 1942 and lived in Milwaukee until they moved to Atherton in 1957.
The Bradfords had four sons and a daughter. In addition to raising her family, she was actively involved in the Palo Alto Junior League, Sacred Heart Preparatory School in Atherton, and Woodside Priory in Portola Valley. She was also an accomplished horsewoman, avid tennis and golf player, and an experienced bridge player, family members said.
The family spent many holidays in Sun Valley, where they were enthusiastic skiers. The Bradfords were married for 27 years until his death from cancer in 1969.
In 1978, she married William R. Hewlett, whose first wife, Flora, died in 1977. In 22 years of marriage, Rosemary and William Hewlett traveled the world, and divided their time between Portola Valley and Sun Valley. They shared common interests in the outdoors, their large families, and multiple charities, family members said.
Mr. Hewlett, who died in 2001, ignited her philanthropic interests. She became actively involved on the boards of Menlo College and the San Francisco Opera Company, and was one of the founding board members of the Peninsula Bridge program, promoting academic and personal success for motivated middle-school students from under-resourced local communities. The Bridge program in particular gave her much satisfaction, family members said.
She was also a member of the order of the Dames of Malta and numerous other clubs and organizations.
The family describes her as a "vibrant spirit who touched all who met her." Until very recently, she continued to travel the world and take holidays with family, close friends, and her caretaker for 17 years, Jose Pinto.
She is survived by sons David Bradford of Tiburon, Robert Bradford of Woodside, Peter Bradford of Portola Valley, and Jeffrey Bradford of Kauai and Sun Valley; daughter Deborah Bradford Whelan of Atherton; eight grandchildren; and her caretakers, Jose Pinto and Elda Chavez and their family.
A private family service and celebration took place Saturday, Nov. 6. Burial will be at the Ketchum Cemetery in Ketchum, Idaho.
The family prefers memorial donations to Peninsula Bridge, 457 Kingsley Ave., Palo Alto, CA 94301.