'Welcome to sleep deprivation society' - Prince William passes on advice to proud new dad Harry
Proud father the Duke of Sussex has been welcomed to the "sleep deprivation society that is parenting" by his older brother, the Duke of Cambridge.
William celebrated the latest addition to the royal family with the quip, and also said he was "absolutely thrilled" about the birth of Harry and Meghan's first child.
The public are expected to be given their first glimpse of the new baby today.
Speaking outside the Cutty Sark in Greenwich, south-east London, yesterday, William was asked how he felt and replied: "Obviously thrilled, absolutely thrilled, and obviously looking forward to seeing them in the next few days when things have quietened down.
"I'm very pleased and glad to welcome my own brother into the sleep deprivation society that is parenting."
Baby Sussex, who has yet to be named, arrived at 5.26am on Monday, weighing 7lb 3oz, and is thought to have been born at the couple's Frogmore Cottage home near Windsor Castle.
But there are some reports claiming the baby was delivered in a London hospital.
Asked if he had any pearls of wisdom for his younger brother, as a father of three, William laughed and said: "Plenty of advice, plenty of advice, but no, I wish him all the best and I hope in the next few days they can settle down and enjoy having a newborn in their family and the joys that come with that."
The Duchess of Cambridge added: "It's such a special time, obviously with Louis and Charlotte just having had their birthdays, it's such a great time of year to have a baby, spring is in the air."
Kate went on to reveal they have not had the chance to see Harry and Meghan's newborn yet and had no clues about his name.
She said: "As William said, we're looking forward to meeting him and finding out what his name's going to be, so it's really exciting for both of them and we wish them all the best. These next few weeks are always a bit daunting the first time round, so we wish them all the best."
Harry was at his wife's side during the birth on Monday and he later confessed he had only had a few hours' sleep, suggesting Meghan had spent much of the night in labour.
The Prince of Wales has also spoken publicly for the first time about the birth, saying he was "delighted" at the arrival of his latest grandchild.
During an official visit to Germany with the Duchess of Cornwall, Charles said: "We couldn't be more delighted at the news and we're looking forward to meeting the baby when we return."
His mother the Queen accepted the congratulations of a Windsor Castle guest who asked "life is good for your Majesty?" following the birth of her latest great-grandchild.
The Queen, who was joined by the Duke of Edinburgh, was hosting a lunch for members of the Order of Merit and smiling, said in reply "yes, thank you".
The infant is believed to be the first mixed-race child born to a senior member of the royal family in centuries and is a reflection of modern Britain's culturally diverse population.
Alexander and Spencer are the new favourite names for the infant with many of the bookies, after the long-term pick Arthur was dethroned in a flurry of betting. Coral has Alexander leading the odds, while a rush of bets has been placed on Spencer, in honour of Harry's mother Diana, Princess of Wales, whose maiden name was Spencer.