Helen Thermoplis is the mother of Amelia (Mia) and the estranged wife of the late Philippe Renaldi, who was the crown prince and heir to the throne of Genovia.
History
In her young adult years in college, she had met and fallen for a handsome man named Philippe Renaldi, whom she later discovered was, in fact, a prince from the country of Genovia. A few years, they married and had one child; a daughter whom they named Amelia, nicknamed Mia. At some point, the two have fallen out and divorced.
The Princess Diaries
Helen calls her fifteen-year-old daughter from her tower room as she is late for school.
The Princess Diaries 2: Royal Engagement
Five years later, she is seen at her 21-year-old daughter's High School graduation next to her husband and is pregnant with her son. She later comes to Genovia to see Mia, now crown princess, and introduces her to her stepfather and infant half-brother Trevor.