Letourneau was born Mary Katherine Schmitz in Tustin, California, to university professor John G. Schmitz and chemist Mary Schmitz., She was known as Mary Kay to her family and called "Cake" by her father. She was the fourth of seven children, raised in a "strict Catholic household."[5][6] When she was 2 years ol, her father began his political career and successfully ran as a Republican for a seat in the state legislature. He held positions as a California state senator and U.S. Congressman and, after changing parties, he ran for president as an American Independent Party candidate in the 1972 U.S. presidential election.
In 1973, Letourneau's 3-year-old brother drowned in the family pool at their home in the Spyglass Hill section of Corona del Mar, California.
In 1982, her father's political career was severely damaged when it was revealed that during his affair with a former student at Santa Ana College, where he had taught political science, he had fathered two children out of wedlock.[9] Her father's affair caused her parents to separate, but they later reconciled. According to friends Mary Kay felt betrayed and thought her mother was a cold person who "drove him to it" by denying her father affection. Schmitz refused to lend financial support or assistance to his illegitimate children who became wards of the state after their mother died.
Mary Kay attended Cornelia Connelly High School, an all-girls Catholic school in Anaheim, California, where she was a member of the cheerleading squad for Servite High School . During her high school years she is reported to have "liked parties, boys, and traveling." She was also a student at Arizona State University and was reported to be a "party-animal
