When the pair ties the knot, it will mark the second marriage for Pratt, whose divorce from actress Anna Faris was finalized last year. Faris and Pratt share a son, 6-year-old Jack.
Want to learn more about Schwarzenegger? Here are five things to know about the 29-year-old author:
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1. She's the daughter of journalist Maria Shriver and actor Arnold Schwarzenegger, the former governor of California.
According to The Sun, she has four siblings: sister Christina, 27; brothers Patrick, 25, and Christopher, 21; and half-brother Joseph Baena, 21.
2. She's related to the Kennedys.
Her maternal grandmother, Eunice Kennedy Shriver, was President John F. Kennedy's little sister, according to Town & Country.
3. She's a self-help and children's book author.
Her titles include "Rock What You've Got: Secrets to Loving Your Inner and Outer Beauty from Someone Who's Been There and Back" (2010); "I Just Graduated ... Now What?: Honest Answers from Those Who Have Been There" (2014); and "Maverick and Me" (2017). She also runs the lifestyle blog KatherineSchwarzenegger.com.
4. She studied communication at the University of Southern California.
She graduated in 2012, Town & Country reported.
5. When did she and Pratt start dating?
Although Pratt didn't acknowledge the relationship on social media until Dec. 13, Schwarzenegger's birthday, rumors began swirling about the pair when they were photographed together on Father's Day. On June 28, E! News reported that the pair had started "talking" about two months earlier.