04/09/2017 2:48 PM IST | Updated 04/09/2017 8:26 PM IST

Duchess Of Cambridge Pregnant: Third Royal Baby For William And Kate

The Duke and Duchess of Cambridge have announced they are expecting their third child.

The Queen and members of both families are said to be delighted with the news. Prime Minister Theresa May greeted the news on Twitter as “fantastic.”

Kate’s brother-in-law, Prince Harry, reacted to the news he will be an uncle once again telling reporters he was “very, very happy.” When asked how she was getting on, he replied: “I haven’t seen her for a while but I think she’s OK.”

The couple are already parents to Prince George, who celebrated his fourth birthday in July, and Princess Charlotte, who turned two in May. The children have travelled on official tours of Poland and Germany with their parents. 

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The Duke and Duchess of Cambrige are parents to Prince George, 4, and Princess Charlotte, 2

Their third child would be fifth in line to the British throne. William, 35, is the eldest son of Prince Charles, the first in line to the throne, and a grandson of the queen. The announcement means Prince Harry is now sixth in line to the throne. 

If the Cambridges’ third child is a boy, he will not be allowed to jump ahead of older sister Charlotte in the line of succession. The Duke of York will move to seventh and Princesses Beatrice and Eugenie to eighth and ninth. The Earl of Wessex is tenth in line of succession. 

Previously, under the ancient rules of male primogeniture, royal sons took precedence over their female siblings, even leapfrogging first-born royal daughters.

But a radical shake-up of the royal succession rules removed discriminatory male bias and came into force in March 2015, affecting babies born after October 28 2011.

As with her previous two pregnancies, the Duchess is suffering from a rare form of acute morning sickness called Hyperemesis Gravidarum. She will no longer carry out her planned engagement at the Hornsey Road Children’s Centre in London on Monday.

Prince George is set to start school on Thursday at an independent school in Battersea, south London. It is not certain if Kate, who has already said she is unsure if George “has any idea what’s going to hit him” will be well enough to accompany her son. 

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The couple at the Lindo Wing of St Mary's Hospital in 2013 with their newborn son George 

The severity of the condition, which affects 3.5 per 1,000 pregnant women, can cause dehydration, weight loss and a build-up of toxins in the blood or urine called ketosis. The 35-year-old is being cared for at Kensington Palace.

It is not known how far along in her pregnancy the Duchess is, though BBC royal correspondent Peter Hunt points out: “For a third time Kensington Palace has had to announce the pregnancy earlier than planned because Kate has acute morning sickness.” It is believed she will be the first senior royal since the queen to have more than two children. 

William and Kate were married at Westminster Abbey in 2011 after announcing their engagement in November 2010. The lavish ceremony was watched by about two billion people around the world. The pair met at St Andrews University. 

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William and Kate visiting the Sunken Garden at Kensington Palace on 30 August. It was transformed into a White Garden, dedicated to the Duke's late mother Princess Diana, who tragically died in a car crash 20 years ago

News of the royal pregnancy comes just days after the Duke and Duchess of Cambridge, alongside Prince Harry, commemorated the 20-year anniversary of Princess Diana’s death with a visit to a memorial garden planted in honour of her. 

In a sign of how the young royals have helped to modernise the House of Windsor, the princes have spoken about the trauma of her death and its lasting emotional impact.