Jessica Simpson Says Daughter's Birthday Wish Was For Grandpa Joe's Cancer Treatment to Work

On Saturday, the singer posted a sweet birthday tribute to her 11-year-old daughter Maxwell Johnson on Instagram, revealing that her daughter's birthday wish was for her grandfather Joe Simpson's bone cancer treatments to be successful.

"On May 1, 2012, my first born, Maxwell Drew Johnson arrived into this life as a sentient being seemingly not of this world. In the purest of form, her mind heart and soul ascended from the grace of heaven to shine in profound ways," Jessica, 42, wrote alongside an adorable mother-daughter photo. "I felt her purpose in my life when I was a kid and I would pray for my future daughter every single day and night."

"I know that most Moms would say please slow down time when their baby turns 11, but I have truly known her my entire life," she continued. "Reading back on 30 yrs of conversations with God throughout my journal entries, it is evident that Maxwell was already living inside of my heart and my purpose."

The fashion designer -- who shares Maxwell, Ace, 9, and Birdie, 4, with husband Eric Johnson -- added that Maxwell's birthday party was "FRANKLIN FARM LIFE HAPPY," before recalling how her daughter made her birthday wish.

"She told me after she blew out HER 11 candles…'I made a wish that was for me and you and actually the whole family,'" Jessica wrote. "I said Maxi it should be your wish and she said 'we have the same wishes Mom.'"

She continued, "3 days later on our way back to Cali she overheard me reading a text from my Dad and asked my mom sitting next to her 'GiGi if my birthday wish came true already can I say it out loud or do I still keep it to myself?' My mom told her to share it with everyone if she wanted to, especially if it had already come true…"

"Maxwell's birthday wish was for her Papa Joe's bone cancer treatment to work. It did," the reality star added. "Thank you Maxi Drew for usin' your wish on our family and most importantly, my Dad."

Jessica ended her post by praising her daughter.

"You are mesmerizing, steadfast, intelligent, passionate, generous, loving, devoted, inspiring, enticing, confident, empathetic, powerful, intuitive, beautiful, DETERMINED, enlightened and FULL OF WONDER," she said. "The faith of a child is what keeps all of us ALIVE."

Jessica's fans took to the comment sections of her post to applaud Maxwell on dedicating her birthday wish to her grandfather.

"Maxwell's soul full of love radiates from her!" a fan wrote. "Thank you for sharing her spirit through the years with your posts and stories and soooo glad to hear about Joe! Happy Bday Maxwell! 💙💙."

"She's has a heart of gold 💛," a person commented, while another said, "This is the sweetest!! This shows how great of a mama you are. 💕 @jessicasimpson."

Jessica's father Joe, 65, was diagnosed with prostate cancer in 2016. In May 2017, his rep shared with People that he was in remission.

Jessica's post on Saturday appears to be the first time she's spoken about her father's bone cancer diagnosis.