Rumer Willis is making every moment with her dad count.

On Sunday, she shared a sweet photo of Willis holding her daughter Louetta Isley, celebrating his first Father's Day since his dementia diagnosis in February.

"Seeing my father hold my daughter today was something I will treasure for the rest of my life," Rumer wrote in the caption. "His sweetness and love for her was so pure and beautiful." 

She continued, "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…."

Rumer , nicknamed Lou, last month, with her partner Derek Richard, whom she also wrote about in the post.

"Happy 1st Father’s Day. Thank you for building a beautiful garden for Lou to play in and eat from," she wrote. 

"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," she added. "Thank you for the greatest girl I could imagine in my wildest dreams. We love you."

Before her daughter’s birth, Rumer told People, "[My parents] are so excited.

My sisters are so excited, and it's so fun to be bringing in the first grandkid in our family, especially because we're such a huge group at this point."

Rumer’s daughter is the first grandchild for Willis and his ex-wife Demi Moore. They also share daughters Scout Willis and . Bruce is also dad to two daughters, Mabel and Evelyn, with his current wife, Emma Heming Willis.

The 34-year-old also shared her parents' best piece of advice prior to the birth of her daughter. 

"You have no control over anything, and just have a lot of grace with yourself," she told the outlet.

The entire family has rallied around Willis in the wake of his , sharing updates and touching moments with the actor.

Last month, Emma posted a video montage of photos showing Willis in dad mode with his daughter Mabel for her 11th birthday.

She also shared an emotional tribute to her husband on his , saying she posted the video of moments together even though looking back can be "like a knife in my heart."

She added, "As much as I do it for myself, I do it for you, because I know how much you love my husband and – don't cry Emma – but it means so much to me, so thank you.

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