Prince George and Princess Charlotte's new sibling will arrive in the spring, Kensington Palace has said.
The third child of Britain's Prince William and wife Catherine, Duchess of Cambridge, is due in April _ the same month the couple will celebrate their seventh wedding anniversary.
"The Duke and Duchess of Cambridge are delighted to confirm they are expecting a baby in April 2018," said a tweet from the palace on Tuesday.
As with her other pregnancies, the 35-year-old duchess is suffering from severe morning sickness; she has kept a low profile since the September pregnancy announcement.
However, on Monday, during a charity event at Paddington Station, her husband confirmed to a royal subject that "she is feeling much better." (A little prenatal math figures the former Kate Middleton is likely four months along, putting her in her second trimester.)
The child will displace William's younger brother, Prince Harry, as fifth in line to the British throne, which has been held by 91-year-old Queen Elizabeth II since the death of her father, King George VI, in 1952. (Her coronation took place a year later.)
Currently, the line of succession names Elizabeth's son Prince Charles, 68, as the heir apparent and her grandson William, 35, and great-grandchildren George, 4, and Charlotte, 2, as her direct successors, respectively.
Princess Charlotte will remain fourth in line to the British throne thanks to a law enacted in 2015 that preserves her succession even in the case of the birth of a younger brother, who previously would have usurped her claim.
