Sarah Ferguson, Fergie Celebrates Birth of Princess Eugenie's New Baby

The Duchess of York previously told PEOPLE that her grandchildren "just follow me around like Peter Pan. I'm 'Super Gran Pan' "

Janine Henni is a Royals Staff Writer for PEOPLE Digital, covering modern monarchies and the world's most famous families. Like Queen Elizabeth, she loves horses and a great tiara moment.

Jo Hale/WireImage; Princess Eugenie Instagram

Sarah Ferguson has a new grandson to love!

On Tuesday, the Duchess of York, who is popularly known as Fergie, celebrated the birth of her daughter Princess Eugenie and son-in-law Jack Brooksbank's new baby boy — Ernest George Ronnie — with a sweet tribute on social media. Ernest was born on May 30, and Buckingham Palace announced the happy news on Monday.

"Amazing.. the importance of Ernest," Fergie wrote on her Instagram Stories. "Thank you," she added with a praying hands emoji, "Soooo much.. clever," continuing, "Eugenie and Jack and August Brooksbank…"

The text was typed over the photo that Princess Eugenie, 33, used to share more about her second son's birth on Instagram. The image showed the sleeping newborn snuggled up in a blue knit hat — a royal hand-me-down from big brother August! — and was followed by a second shot of 2-year-old August gently touching his baby brother's head.

Sarah Ferguson Instagram

RELATED: Princess Eugenie Welcomes Second Son with Husband Jack Brooksbank — and Shares His Name!

"Jack and I wanted to share the news that we had our little boy, Ernest George Ronnie Brooksbank on 30th May 2023 at 8.49 weighing 7.1lbs," Princess Eugenie captioned the snaps. "He is named after his great great great Grandfather George, his Grandpa George and my Grandpa Ronald. Augie is loving being a big brother already."

Ernest's middle names honor Queen Elizabeth's grandfather King George V, Jack's father George and Eugenie's maternal grandfather Ronald, who is Fergie's father. Ronald Ferguson, who died in 2003, was the longtime polo manager for Prince Philip and King Charles.

Princess Eugenie/instagram

Baby Ernest takes his place as 13th in the line of succession to the British throne. He is also the first of Queen Elizabeth's great-grandchildren to be born following her death in September and the third grandchild for Prince Andrew and Fergie.

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The Duke and Duchess of York, both 63, divorced in 1996 after a decade of marriage but remain close today. Prince Andrew and Fergie were already grandparents to August and Princess Beatrice's 1-year-old daughter Sienna Elizabeth, whom she shares with husband Edoardo Mapelli Mozzi. Edo is also dad to son Christopher Woolf, whom he shares with ex-girlfriend Dara Huang.

Princess Eugenie/instagram

While recently speaking to PEOPLE about her latest historical fiction novel A Most Intriguing Lady, Ferguson said she cherished everything about being a grandmother.

"One, I'm really proud of my girls. Two, I have very good grandchildren," said the Duchess.

"They just follow me around like Peter Pan. I'm 'Super Gran Pan.' Whenever they see me, they laugh. They think I'm very funny," she added.

Buckingham Palace announced that Princess Eugenie was pregnant in January, and the Duchess celebrated her daughter's growing family with an Instagram tribute the day after.

"So happy for my girlie," she captioned the snap, where she held Eugenie close in a hug.

Fergie also hinted that Princess Eugenie's new addition was imminent earlier this month in an interview with ¡HOLA! TV. "We don't know what it is yet," the Duchess said of the sex, Hello! reported. "But the baby is due by the end of May, I think. So it's any minute now."

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After seven years of dating, Princess Eugenie and Jack, 37, got married in October 2018. Their first son August was born in February 2021, and the family of three became four by welcoming Ernest.