The baby, the eighth great-grandchild of 93-year-old Queen Elizabeth, the world's longest-reigning monarch, will not automatically be a prince or a princess or be known as "His Royal Highness" unless the Queen issues a decree.
The actress is closely tracking the developments since news broke this morning that the Duke and Duchess of Sussex, Prince Harry and Meghan Markle, have given birth to a baby boy. The American actor, who is now performing in the London West End show, Death of a Salesman, took to Twitter earlier last month to offer his blessings to Markle ahead of her due date. Harry said on Monday the couple were still mulling over their choice.
Royal commentator Omid Scobie tweeted: "It will be a quiet day in terms of announcements but tomorrow's photo call is not far away". The Daily Mail claimed that the birth came precisely three minutes later than that.
Will the royal baby be a prince?
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"It's been insane", Amy Jones, a spokeswoman for Paddy Power bookmakers, told AFP. Although the new parents are ready to present their child, it is yet to be confirmed whether they have decided on their son's name. United Kingdom royal names are normally chosen from a relatively restricted pool of those used by past kings and queens.
In Prince Harry's case, the Queen didn't change the rules again to allow his children to be referred to as His or Her Royal Highness and a prince or princess.
This Monday, May 6, William, 36, and Kate, 37, reposted Meghan Markle and Prince Harry's "It's a boy" image on their Kensington Royal Instagram account. The baby news was greeted warmly in the United States: on the border with Canada, the Niagara Falls waterfall was lit up in blue.
In the U.S., the former first lady of the United States, Michelle Obama also sent her and Barack's congratulations. Meghan's estranged father Thomas did not attend either, creating a lingering scandal.
The Duke and Duchess of Sussex have just had their first baby together, but they haven't revealed a name yet.
Among the well-wishers were cast members of hit U.S. legal drama, Suits, who tweeted their congratulations to Markle, who previously played the sassy paralegal-turned-lawyer Rachel Zane in the series before she Wednesday Harry and became the Duchess of Sussex.
Adams posted on Twitter: "Just heard that the world just got heavier by seven pounds and three ounces".