The Duke and Duchess of Sussex donated $5,000 in Archie and Lili's name following the tragic death of nine-year-old George Zafjen.
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The former model, 42, took to her Instagram to share the devastating update with her followers.
Beneath a sun-drenched photo of George receiving a piggyback from his twin sister, Kelly penned: "My sweet baby boy. My world is shattered into a million pieces. I have little ability to breathe. Walk. Function. Sit. Stand. You were the light of my life. Your smile made the room so bright and your heart was the most perfect and sweetest."
Kelly penned an emotional tribute to her son George
Utterly heartbroken she added: "You left this Earth and left behind so many people who loved you. I don't know how I'm able to go on. How I can function. How I can be the light and have joy ever again but I'm going to try. Try hard for your beautiful twin sister."
Former model Kelly is an entrepreneur and co-founder of Alliance of Moms. The community-based organisation supports pregnant and parenting teens in LA's foster care system by equipping them with the tools they need to build a better future.
While the Sussexes' connection to Kelly remains unclear, it is thought that Meghan may have been friends with the Zafjen family. Meghan's ex-husband Trevor Engelson and his wife Tracey Kurland similarly made a $1,000 donation suggesting that Meghan and Trevor may have known the family during their relationship.
Trevor and his wife also made a sizeable donation
The GoFundMe page was created by family friend Kate Jefferson who set up the fundraiser on behalf of Kate and her grieving family. In the description box, she wrote: "My name is Kate and I’m raising funds for the Zajfen family so that they may grieve the loss of their sweet angel boy, George.
"He was the happiest, kindest boy that walked the earth. George's heart was compassionate, his smile contagious, and his love for his twin sister and parents was palpable. This unexpected loss is beyond devastating and the Zajfen family will need time to even begin to heal."
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