Sarah Ferguson gushes about being a grandmother in heartfelt open letter to Beatrice and Eugenie

The author has released a heartfelt open letter to her daughters

Sarah Ferguson has expressed her joy over becoming a young grandmother in a heartfelt open letter to her daughters about motherhood.

In the letter, published in Good Housekeeping, the 61-year-old said her children, Princess Beatrice and Princess Eugenie, have made her "life complete" and how she's loved watching their journey into motherhood.

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WATCH: Sarah Ferguson speaks about her grandson August

Eugenie, 31, welcomed son August with husband Jack Brooksbank in February, while 33-year-old Beatrice is expecting her first child with husband Edoardo Mapelli Mozzi this autumn - she is also stepmother to his son Wolfie.

MORE: Sarah Ferguson and Edoardo Mapelli Mozzi react to James Middleton's wedding joy

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"From the time you were wee tots, you made my life complete. I look at how full of humility, laughter and joy you are in your hearts, and I marvel at you both," she wrote.

"Now, in you as mothers, I see strength, courage and steadfastness, integrity and goodness, and the way you embrace every challenge and moment. It is an extraordinary feeling when your child becomes a mother."

Sarah has released an open letter to her daughters

On being overwhelmed with emotion, Sarah continued: "Suddenly my little girlies have their own little ones... such a feeling to get used to. But if I do cry or tear up as you drive away, it is only because I am so proud of you."

READ: Sarah, Duchess of York on being a grandmother to 'phenomenal' baby August

It has been just us for 33 years, but now you are creating your own families, and I couldn't be happier for you both and my magnificent sons-in-law, Jack and Edo."

Speaking about being a "young" grandmother, Sarah noted: "Being 61 makes me a young grandma, and I love it. I smile from my heart every day, because that is how it feels to be a granny.

"I have so many fun ideas of things to do with my grandchildren, and of course they’re a perfect new audience for all my children's books."

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