A similar incident went down in October 2018 with Beatrice's sister Princess Eugenie - at Eugenie's wedding to Jack Brooksbank, Harry and Meghan shared the news that they were expecting their first child with the family.
"It did not go down particularly well with Eugenie, who, a source said, told friends she felt the couple should have waited to share the news," an extract from explosive biography Finding Freedom revealed.
Days later on their Australian royal tour, the news was confirmed to the world and Duncan added that Beatrice's announcement means she and her sister are now "having the last laugh."
"You’d like to think the royals were above petty point scoring.
"But Eugenie was genuinely upset Meghan stole some of the limelight on her big day.
"The Royals are human beings and it does feel the York sisters are having the last laugh."
Harry and Meghan seemed to steal Eugenie and Jack's thunder once again when they announced that they were expecting their second child just days Eugenie and Jack welcomed their son August.
In the official statement released on Wednesday evening, the Queen, who has had a tough year what with the death of her husband Prince Philip, was said to be "delighted" with the baby news.
"Her Royal Highness Princess Beatrice and Mr Edoardo Mapelli Mozzi are very pleased to announce that they are expecting a baby in autumn of this year," it read.
"The Queen has been informed and both families are delighted with the news."
With Harry and Meghan's second child due in the coming months, Beatrice and Edo's child will be the Queen's twelfth great-grandchild and will be eleventh in line to the throne.