Blossom Rock was born on August 21, 1895, in Philadelphia, Pennsylvania. She was the second of three daughters born to Anna May (née Wright; July, 1871 – May 16, 1947) and Daniel MacDonald (April, 1869 – August 8, 1924). As a youth, she performed on the vaudeville stage with her younger sister, Jeanette, and later with her husband, actor Clarence Warren Rock, whom she married in September 26, 1926 Manhattan NY CN # 24447. They had no children. Rock had an elder sister, Elsie MacDonald, who had also been a vaudeville performer and then operated a dance school until 1962.