LONDON - Catherine, Duchess of Cambridge, or Kate, as she's known to most of the world, delivered she and Prince William's third child on Monday; a little brother for Prince George and Princess Charlotte. Kensington Palace confirmed in a tweet that both mother and baby were doing well, and that Prince William was there for the birth.

Kate arrived Monday morning  in "the early stages of labor" at St. Mary's Hospital in London and was admitted to the Lindo Wing, where she had already given birth twice. She and William arrived together by car. 

The new prince's name was not immediately announced.

Known simply as Kate Middleton before her royal life began, the Duchess announced she was pregnant with her third child after missing a royal engagement in September. As with her other two pregnancies, she suffered from hyperemesis gravidarum, or acute morning sickness.

The couple's second child, Princess Charlotte, began attending nursery school in London in January at the age of two. She turns three in May. Her big brother Prince George is four and began school in September last year.

Growing royal brood

The baby boy is now fifth in line to the British throne, after grandfather Prince Charles, father William, Prince George and sister Princess Charlotte. He is Queen Elizabeth II's sixth great-grandchild.

Monday was already special in the U.K.; April 23 is St. George's Day, which honors the patron saint of England. Kate spent about 10 hours in labor with Prince George, but her second child, Princess Charlotte, was delivered after less than three hours.

CBS News correspondent Roxana Saberi reports that, like all royal babies, the new addition to the family can expect to melt hearts and make headlines when first seen by the public on the steps of the Lindo Wing. But after that, he won't likely be seen very often; William and Kate have closely guarded their children's privacy.

The British royal family is set for a big year, with Prince William's brother Prince Harry set to marry American actress Meghan Markle on May 19 at Windsor Castle, outside London.