Mary Katherine Schmitz was born in 1962 in Tustin, California, the daughter of Mary E. (née Suehr), a former chemist, and John G. Schmitz (1930–2001), a community college instructor and politician. 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. " When Letourneau was two years old, her father began a 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, winning a special election for an unexpired term in 1970 and the general election later that year. After a primary defeat in 1972, he changed parties and ran for president as an American Party candidate in the 1972 U. S. presidential election. In 1973, Letourneau's three-year-old brother drowned in the family pool at their home in the Spyglass Hill section of Corona del Mar, California, while she played with another brother in the shallow end.