Harmon took to Instagram to share the news with several photos of her blended family in matching holiday sweaters.
"Marry, Marry Christmas!! ❤️?? ," she wrote on Wednesday. "#moderndaybradybunch #blessed #grateful #family #christmas2019 Wishing you the most wonderful holiday from our family to yours!"
In one shot, Vaughan popped the question to a shocked-looking Harmon who was sitting on her steps.
The 46-year-old actor known for his work on The Young and the Restless, General Hospital, and Days of Our Lives also shared the pics to his own social media account, adding in a few extra shots including a close-up of the ring. "Well...that was FUN!!!" he wrote.
This is the second marriage for both Vaughan and Harmon. Vaughan was previously married to Touriya Haoud from 2006 to 2014. They share three sons. Harmon was also previously married from 2001 to 2016 to Jason Sehorn, who popped the question by surprising the actress during a taping of The Tonight Show with Jay Leno. They share three daughters.