The Duke of Cambridge has welcomed his younger brother to the “sleep deprivation society” as senior royals spoke publicly of their delight at the latest addition to the family.

The Duke and Duchess of Sussex are expected to present their baby son to the world on Wednesday and could announce the name they have chosen.

Two days after giving birth, Meghan, 37, is expected to join Harry, 34, at a small photocall to introduce the newborn seventh-in-line to the throne.

Royal baby: Meghan, Duchess of Sussex, gives birth to boy Read more

Asked to comment on the birth of his nephew, Prince William said: “Obviously thrilled, absolutely thrilled, and obviously looking forward to seeing them in the next few days when things have quietened down.”

He added: “I’m very pleased and glad to welcome my own brother into the sleep deprivation society that is parenting.”

The baby’s paternal grandfather, Prince Charles, said during an official visit to Germany: “We couldn’t be more delighted at the news and we’re looking forward to meeting the baby when we return.”

As one member of the crowd at Brandenburg Gate offered congratulations on the new grandchild, Charles replied: “Thank you, I’m collecting a rather large number of them.”

Baby Sussex was born at 5.26am on Monday, slightly overdue, weighing 7lbs 3oz. Buckingham Palace has refused to give any details of where the baby was delivered, and has not confirmed or denied reports that Meghan gave birth in an exclusive private London hospital, possibly the Portland.

Asked if he had any advice to impart to Harry, William, a father of three, laughed and said: “Plenty of advice, plenty of advice, but no, I wish him all the best and I hope 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: “We’re looking forward to meeting him and finding out what his name is going to be. It’s really exciting for both of them. These next few weeks are always a bit daunting the first time round so we wish them all the best.”

The new parents’ desire for absolute privacy meant Buckingham Palace only announced Meghan had gone into labour eight hours after she had already given birth.

At the couple’s request, no details of the medical team assisting with the birth were included on the formal announcement posted on a gilt easel on the forecourt of Buckingham Palace.

Harry and Meghan had already decided to keep arrangements for the birth private, amid speculation they had opted for a home birth.

Harry attended the birth, and Meghan’s mother, Doria Ragland, who had flown from her Los Angeles home to support her daughter, is staying at their Windsor residence, Frogmore House.

The child may be only two days old but he is already entitled to a title. Harry and Meghan could choose for their son to be known as the Earl of Dumbarton, one of the subsidiary titles bestowed on Harry by the Queen upon his marriage.

The baby is not automatically born a prince or entitled to be styled HRH, his royal highness. George V, the baby’s great-great-great grandfather, limited the use of the style HRH in 1917, confining it to the children of the sons of the sovereign and their spouses.

But it is ultimately in the gift of the Queen, who can step in and issue a Letters Patent under the Great Seal of the Realm to make the baby boy a prince. This she did with the three offspring of the Duke and Duchess of Cambridge.

The new baby is automatically promoted to an HRH when his grandfather Prince Charles becomes king, as the title is automatically conferred on a child of a son of a sovereign.

The baby could also be known as Lord (first name) Mountbatten-Windsor, or, if the couple decide against any titles, simply Master (first name) Mountbatten-Windsor.

George V changed the family name from Saxe-Coburg and Gotha to the bland, more acceptable “Windsor” at the height of the first world war. It was after the Queen’s marriage to Prince Philip that the “Mountbatten” – itself an anglicised version of the more German Battenberg – was added by the monarch to fulfil her husband’s deep-rooted desire for his descendants to bear his family name.