jean Kasem was one of five children, with siblings Jeanette, Shirley, Joan and Tommy Thompson, of Irene Celia Thompson (1919-2008) and Herbert Owens Thompson Sr. (deceased). She lived in Portsmouth, New Hampshire, before her civil-servant father moved the family to Guam in 1963 to help stop her recurring pneumonia.
She attended the University of Guam at age 16, but after marrying a U.S. Navy lieutenant when she was 17, she left to work as a waitress and saleswoman on U.S. military bases throughout the Pacific Ocean to which her husband was posted.
The marriage lasted six years. Kasem then moved to California and unsuccessfully attempted to find work in broadcast journalism. Frustrated, she joined an acting workshop and soon found roles on such TV series as Matt Houston, Fantasy Island and Alice.