In the post Eugenie shared two pictures of baby Ernest, one of him sleeping in his moses basket while wearing a knitted blue and white hat and another showing big brother August sweetly stroking his head.
She commented underneath explained the meaning behind each of his three names, as his middle names were inspired by several family members, including a former king.
Eugenie wrote: “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.
“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 great-great-great grandfather George is George V, the grandfather of the late Queen, who was on the throne from May 1910 until his death in December 1936, and had Ernest as one of his middle names.
His first middle name George is tenderly for Jack’s late father and the baby’s grandfather George Brooksbank, who sadly died in November 2021 at the age of 72 following a long battle with Covid.
The second middle name Ronnie is after Ronald Ferguson, Fergie’s late father known as the “galloping major” who died in 2003.
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Baby Ernest, a third grandchild to Fergie and Prince Andrew and a second nephew for Princess Beatrice, is 13th in line to the British throne.
His arrival bumps Prince Edward down to 14th and Princess Anne down to 17th, although she was third in line at the time of her birth.
He will not receive a title or HRH status as he is not a grandchild of the current monarch, his great-uncle King Charles.
In February 2021 Eugenie and Jack, who married in October 2018, announced the arrival of their first child August Philip Hawke, who is also named for a family member.
His first middle name is after Eugenie’s grandfather Prince Philip, who passed away in April that year just weeks after August was born on February 9.
In a documentary released in September 2021 Eugenie got emotional as she revealed Philip was able to meet baby August shortly before his death.
She said: “We named August, August Philip because grandpa has been such a huge, inspiring character in my life.
“I brought little August to come and meet him and told him that we had named him after him and it was such a lovely moment.”