The 34-year-old describes the moment as 'something I will treasure for the rest of my life.'
"Fathers to the old and new," Rumer captioned an Instagram carousel. "Seeing my father hold my daughter today was something I will treasure for the rest of my life. His sweetness and love for her was so pure and beautiful. Papa I’m so lucky to have you and so is Lou. Thank you for being the silliest, most loving, coolest Daddio a girl could ask for. Best Girl Dad in the game…."
The Die Hard actor is beaming in one shot, posing with his arm around Rumer as she holds baby Louetta while leaning into him. In another snap, Bruce sweetly holds the child to his chest.
The precious moment comes amid Bruce's heartbreaking battle with frontotemporal dementia, a progressive neurological disorder that impacts both cognition and behavior. Bruce was diagnosed with the disorder last year, and as a byproduct, aphasia, a brain-mediated inability to speak or to understand speech.
Rumer also paid tribute to her partner, musician Derek Thomas, on his first Father's Day with their daughter.
"Thank you for building a beautiful garden for Lou to play in and eat from. 🌱 Thank you for filling the house with music for her to hear 🎶 Thank you for all the late night diaper changes and silly faces. I’m so grateful our girl has a papa that loves her so much and someone so goofy and weird so she knows that’s ok for her to be too. Thank you for the greatest girl I could imagine in my wildest dreams. We love you 🧡" she wrote.
The baby is the first grandchild for both Bruce and Demi Moore, who were married for more than a decade before their split in the late '90s. Together, they share daughters Rumer, Scout, 31, and Tallulah, 29.
Today, Bruce is married to Emma Hemming Willis and together they share daughters Mabel, 11, Evelyn, 9.
Heming has been working to bring awareness to frontotemporal dementia and has been candid about the ups and downs of being a full-time caretaker for her husband. In May, the 44-year-old announced she was launching a brain health brand.