The 33-year-old royal has revealed she and her husband Jack Brooksbank welcomed Ernest George Ronnie – a sibling for 2-year-old Ronnie – into the world on May 30, weighing 3.2kg (7.1lbs).
The princess shared a close-up photo of the newborn and another of the baby being affectionately stroked by his big brother.
She captioned her post: “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.”
Eugenie, who is the daughter of Prince Andrew and his ex-wife Sarah Ferguson, Duchess of York, explained the origins of the little boy’s name.
She said: “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.”
News of Ernest’s birth comes three weeks after Ferguson revealed her daughter was due to give birth “any minute now”.
Asked about the baby, Ferguson, told “¡HOLA! TV”: “Well, we don’t know what it is yet. But the baby is due by the end of May, I think. So it’s any minute now.”
The “Her Heart For A Compass” author – whose other daughter, Princess Beatrice, has 7-year-old stepson Wolfie and daughter Sienna, 20 months, with husband Edoardo Mapelli Mozzi – thinks she is “one of the best” grandparents ever.
Questioned on what she is like as a grandmother, she said: “Well, the thing is, is that I’ve written 48 children’s books and I’ve flown helicopters, Budgie, the helicopter, and Little Red. And so, I’m wanting to actually write a book about a football, now.
“Hence, I’m in the room with footballs and I’m going to write about a bouncy football.
“But anyway, I’m probably one of the best grannies ever. The best abuela (Spanish for gran) ever because I think like a 3 year old.”