Sister of Demi-Leigh Nel-Peters, Tim Tebow's fiancee, dies suddenly at 13

Tim Tebow and his fiancee, Demi-Leigh Nel-Peters, suffered a tragic loss this weekend.

Nel-Peters' 13-year-old sister, Franje, who brought the couple together through Tebow's "Night to Shine," which celebrates people with special needs, died suddenly on Saturday after battling an extremely rare lifelong condition called cerebellar agenesis, according to the South African.

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“My little Princess, Angel on Earth, biggest joy and baby sister, Franje, passed away earlier today,” Nel-Peters wrote in an Instagram post.

Franje was born without a cerebellum, severely limiting her motor functions, or the ability to walk, talk, and develop as a child.

“Our hearts are aching beyond measure but I am grateful knowing she’s forever relieved of the pain she experienced on earth," Nel-Peters added. "She’s laughing, running and playing in heaven just like we always hoped she would on earth. She’s free! Thank you for all your prayers, love and support.”

The 2017 Miss Universe and humanitarian worker ended the message in their South African native language that translates: “Love you always my Sussa and someday we'll be together again!”

The New York Mets minor leaguer shared a photo of the three of them offering his prayers and love to Nel-Peters' parents.

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"Our loss but heavens gain," Tebow wrote. "So grateful for the hope we have of being reunited with the ones we love through our Heavenly Father."

The pageant community also reached out to the former Miss South Africa.

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"Love you dearly Dems," former Miss USA Sarah Summers said. "You're full of grace even in the hardest times."

And former Miss Universe winners Iris Mittenaere and Pia Wurztbach also shared their condolences.