The news of Jaimi's death comes just months after mum Lisa shared a heartwarming tribute to her daughter for her birthday.
"Happy birthday to our beautiful Jaimi... 33 today ! Our first born. Really.... where have all those years gone ! Have a lovely day bubba. We all love you so much," she captioned a series of photos of Jaimi through the years in June.
The post has since been flooded with messages of condolence from fans.
"Thinking of you all at this very sad time," one follower commented.
"I am so sorry Lisa and family. Just heartbreaking," wrote another.
Lisa and Grant, who split in 2009 after 23 years of marriage, also share daughter Morgan Gruell and son Jett Kenny.
Jaimi also has a seven-year-old half-sister, Trixie Box, whom Grant shares with radio and TV personality, Fifi Box.
Morgan is currently pregnant with her second child, Lisa and Grant's second grandchild, and the former swimming champ, who has since married Elvis impersonator Mark Tabone, shared the exciting news in May.
“YES!! I'm going to be a Granny again,” Lisa captioned a sweet snap of her three-year-old grandson Flynn cuddling a toy and adding, “Getting ready to be a big brother.”
“Congratulations Morgan and Ryan. I can't wait for your little family to grow.”
Our thoughts go out to Lisa, Grant and the entire family during this difficult time.