The 60-year-old actor and 52-year-old actress saw Rumer make her Broadway debut in Chicago at the Ambassador Theatre. The former couple's younger daughters, Scout Willis and Tallulah Willis, were also on hand to support their sister.
Rumer will portray aspiring star Roxie Hart for a seven-week engagement ending Nov. 1. The 27-year-old actress previously appeared in Love, Loss and What I Wore off-Broadway and For the Record Live's Dear John Hughes.
"These people are everything to me," she wrote on Instagram. "I would never have made it to that stage without you guys. Thank you to my amazing parents for supporting me my whole life and thru all my crazy ideas and adventures and pushing me to be the best version of myself and to my sisters for being my partners in crime, my confidants and for always letting me be my goofy unabashed self. I love you all."
"An indescribably special experience to see you tonight on broadway @ruelarue I love you so much sestra," Tallulah captioned a photo with her sisters. The girls' stepmother, Emma Heming, added, "Beaming with pride! Still buzzing from her performance last night. You never fail to amaze us @ruelarue."
Willis and Moore were married from 1987 to 2000, and went on to wed Heming and Ashton Kutcher, respectively. The actress and Kutcher have since divorced, but Willis and Heming are still together and share two daughters, 3-year-old Mabel and 1-year-old Evelyn.
Rumer appeared on such shows as 90210, Pretty Little Liars and Hawaii Five-0 before partaking in Dancing with the Stars season 20. She and professional dancer Val Chmerkovskiy won the competition in May, and the actress went on to perform on the Dancing with the Stars: Live! tour.