The Duchess of York penned an emotional open letter to Beatrice and Eugenie, published in Good Housekeeping, outlining heartfelt advice to her beloved daughters. She paid homage to both Beatrice and Eugenie, praising their "courage, strength and integrity", while marvelling at the fact they are starting their own families. Eugenie, 31, and Jack Brooksbank welcomed their son August Philip Hawke into the world in February.

       Beatrice, 33, is expecting her first baby with husband Edoardo Mapelli Mozzi this autumn.

       She is also the step-mother to her husband's two-year-old son Christopher 'Wolfie' Woolf.

       While celebrating her daughter's entry into motherhood, the Duchess was eager that they remained true to her own guiding principle as a parent.

       "Nothing gives me more pleasure than watching you be incredible mothers," she wrote.

       "When your children walk on their own journeys, please teach them to be authentic to themselves, like I taught you.

       "Tell them to always try to turn to joy —to see nature, hear the birds sing, feel the rain droplets that make trees smile.

       READ MORE: Sarah Ferguson and Beatrice's husband Edo share emotional tributes

       "Believe in fairies and the magic of every day.

       "Never give up on the road to smiles and rainbows, and remember the saying 'This too shall pass, like the clouds in the sky'."

       The Duchess of York grew up without her mother after her parents divorced in 1974.

       DON'T MISS

       Prince Andrew 'wants to wed Fergie again' [Reveal]

       Fergie's 'off-the-cuff remark' sparked open season with press [Spotlight]

       Sarah Ferguson 'thrilled' to spend time with Queen at Balmoral retreat [Insight]

       In an article for the Sun, royal expert Ingrid Seward wrote that Fergie felt unloved and insecure when her mother fled the family nest and blamed herself for her mother's decision.

       Fergie is the author of a number of very popular children's books, including "The Adventures of Charlie, Blue and Larry the Lamp Post" and "Budgie the Little Helicopter".

       She has promised to write a book a month over the course of the next year "to create a lovely library for my grandchildren".