BALDWIN: Britain celebrating news that a brand-new royal is on the way. Prince William, his wife, Kate, celebrating their third child. The baby joins big brother and sister, Prince George and Princess Charlotte. The new baby will be fifth in line to the throne. CNN's Erin McLaughlin has more on the big announcement -- Erin?</s>ERIN MCLAUGHLIN, CNN CORRESPONDENT: Brooke, Kensington Palace announced the happy news this morning. The announcement made after the Duchess of Cambridge had to cancel an appearance at a royal event due to acute morning sickness. It was at that point that both she and Prince William decided to announce this news before the 12-week mark, decided to be open with the public about what was going on. Acute morning sickness is something that she suffered from during her previous two pregnancies. In fact, you may remember, with Prince George, she was actually treated in hospital. This time around, as with Princess Charlotte, she's being treated at Kensington Palace. Doctors, no doubt, monitoring her. The key concern with acute morning sickness is dehydration. We understand from Prince Harry, who is out and about in London today, that she's doing just fine. Take a listen.</s>UNIDENTIFIED REPORTER: How are you feeling about the news you'll be an uncle again?</s>PRINCE HARRY: Fantastic. Great. Very, very happy for them.</s>UNIDENTIFIED REPORTR: How is your sister-in-law doing?</s>PRINCE HARRY: I haven't seen her for a while, but I think she's OK.</s>MCLAUGHLIN: Prince Harry currently fifth in line for the throne. Once this baby is born, he'll be sixth. We understand, once the Duchess of Cambridge is feeling better, she'll be back to her royal duties -- Brooke?</s>BALDWIN: Erin, thank you so much. Ahead here on CNN, U.N. Ambassador Nikki Haley says North Korea is, quote, "begging for war." So what, if anything, can be done to stop them?
Prince William & Kate Expecting Baby.