Like any proud new grandmother, Sarah has been expressing her excitement over her baby grandson on her YouTube series, Storytime With Fergie and Friends.
In Wednesday's video, the Duchess read Baby On The Way by Hannah Davison, Marco Palmieri and Flicka Williams.
Before reading the children's book, Sarah, waving a magic wand, excitedly said: "Hello, magic dust is in the air!"
She added: "Very exciting times, and I'm a granny!"
Eugenie shared the first image of her son on Instagram
In a statement announcing the royal birth's birth, Buckingham Palace said: "Her Royal Highness Princess Eugenie was safely delivered of a son today, 9th February 2021, at 0855hrs at The Portland Hospital. Jack Brooksbank was present. The baby weighs 8lbs 1oz.
"This is Princess Eugenie and Jack Brooksbank's first child, The Duke of York and Sarah, Duchess of York's first grandchild, and the ninth great-grandchild for The Queen and The Duke of Edinburgh. Her Royal Highness and her child are both doing well."
Jack and Eugenie were pictured leaving the hospital with their baby son
On Pancake Day, otherwise known as Shrove Tuesday, Sarah shared a fun boomerang-style video on Instagram of her successfully flipping a pancake, surrounded by some of her children's books, and at HELLO! HQ we couldn't help but wonder if one of them is a possible hint about her baby grandson's name.
One of the bookies' favourites for the royal tot is Arthur and in the corner of Sarah's video, her book Arthur Fantastic can be seen.
While it might be purely coincidental, it's the only boy's name that can be seen among the titles of her children's novels.