THE Duke and Duchess of Cambridge are expecting a third child who will be fifth in line to the British throne.Kensington Palace announced the news on Monday, saying that the Queen and rest of the Royal Family are “delighted”.The Duchess is suffering from an extreme form of morning sickness, hyperemesis gravidarum, as she did with previous pregnancies.She has been forced to cancel her planned engagement at a London children’s hospital today and is being cared for at Kensington Palace.The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting their third child