Princess Beatrice and Princess Eugenie's children have been praised by Sarah Ferguson as "inspiring".
The Duchess of York is travelling to Melbourne, Australia Global Citizen NOW from March 4 to 6, where she will meet with young people to discuss the climate crisis.
Fergie, 64, spoke about how her four grandchildren, Wolfie, Sienna, August and Ernest are her inspiration.
Writing on Instagram, she said: "Ilook forward to listening to [young leaders], learning from them, and contributing whatever voice I have to speak up for the future of our planet.
Sarah has four grandchildren through Beatrice and Eugenie
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"My parents always highlighted the need to champion the quiet voice of Mother Nature, and now even more so since becoming a grandmother I’ve become acutely aware of my responsibility, and that of my generation, to do everything we can to improve the state of the world we are leaving for our grandchildren."
Hugh Jackman and Charlie Puth will be present at the Global Citizen NOW action summit, of which Sarah is a co-chair.
This comes as the duchess recently urged people not to skip their health check-ups, warning that "days could make the difference between life and death" as she marked Cancer Prevention Action Week.
Sarah was diagnosed with malignant melanoma, a form of skin cancer, in January. This came less than a year after facing breast cancer.
Eugenie shared some snaps of Ernest when he was born and his three-year-old brother August
Instagram / Princess EugenieFergie said her diagnosis was a shock but she was "in the best hands and feeling positive".
She said: "After undergoing a mastectomy and reconstruction, I could only hope that I was in the clear, which is why a new diagnosis of skin cancer came as a shock.
"I'm now in the best hands and feeling positive with the support of my family."
The duchess travelled to the US earlier this month to take part in several charity events.
Sienna Mapelli Mozzi standing next to her son August Brooksbank.Instagram / Princess Eugenie
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Sarah Ferguson urged Brits to check for signs of cancer following diagnosis. ReutersShe attended a luncheon at Palm Beach in honour of the Cancer Alliance of Help and Hope, where she gave a touching speech.
Sarah paid tribute to her former brother-in-law, King Charles, who is currently undergoing cancer treatment of his own.
She said: "I want to thank you all for your kindness in supporting my family members who are going through a hard time, and we wish everyone well, every family in the world, that has been diagnosed or who is going through a difficult time we wish them well.
"And of course, my brother-in-law, we wish you well, keep fighting on."