It's a bittersweet time for Kimberly Williams-Paisley! The Father of the Bride actress is gearing up to drop the first of her kids off at college for the first time, and is looking back to their most tender childhood moments because of it. The Where the Light Gets In: Losing My Mother Only to Find Her Again author is a mom to sons William Huckleberry, 18, and Jasper Warren, 16, who she shares with her husband Brad Paisley, who she married in 2018. In honor of William's forthcoming college move, Kimberly, 53, took to Instagram and shared a photo of an old letter that he wrote her when he was seven years old. The letter reads: "Com visit me in calij. Love huck," and: "You promes," which in turn Kimberly wrote in her caption: "I promes I promes I promes," with a red heart and crying emojis. She added in hashtags: "college drop off," and "he wrote this when he was 7," plus: "still counts," and fans were quick to take to the comments section under the post and gush over it. "Oh my goodness. I love that you kept this," one wrote, as others followed suit with: "Love this so much! Just dropped my boy off on Saturday to start a whole new life! The pages keep turning… Good job mama!" and: "Oh goodness. The sweetest. I'm right there with you. Drop my first one off tomorrow," as well as: "Oh bless it — this is so dear." LeAnn Rimes, Kimberly's new co-star in the forthcoming 9-1-1 spin-off 9-1-1: Nashville, also wrote: "Omg… the sweetest." Fittingly, Kimberly is based in Nashville, Tennessee, where the new show is filming. She stars as Cammie Raleigh, a 911 dispatcher, opposite Chris O'Donnell, Jessica Capshaw, Michael Provost, Hailey Kilgore, Juani Feliz, Hunter McVey, Kane Brown, and Tim Matheson. The show, which will premiere on ABC on October 9, is already filming. Jessica, recently speaking with her Grey's co-star Camilla Luddington on their podcast Call It What It Is of being on set, said of Kimberly: "I love [her] so much," and revealed: "I've already had dinner with her multiple times. She and I have gone on a hike. She's so awesome." She also gushed about her on-screen husband Chris, who she has known for over two decades since they worked on The Practice together. "I adore [him] and have known him for a really long time," she said, recalling: "I remember feeling like a baby actress, and I remember feeling like he was not a baby actor. He was accomplished, and I'd seen so many movies he'd done that I love so much." Chris will be starring as Captain Don Sharpe, while Jessica will play his on-screen wife Blythe, and their son Ryan will be played by Michael. "My first work was with Michael, and I adore him," she also said of her on-screen son. "I feel so, so lucky to have such a talented and kind and just awesome person to work with."