The Duke and Duchess of Sussex are the parents of a baby boy, born weighing 3.3kg (7lb 3oz). Prince Harry said his new son was “absolutely to die for”.

Meghan was safely delivered of the seventh in line to the throne at 5.26am on Monday, Buckingham Palace announced.

The new royal, an eighth great-grandchild for the Queen, 93, and the Duke of Edinburgh, 97, was “a little bit overdue”, according to Harry, who revealed they were “still thinking about names” and confessed he had only had “about two hours’ sleep”.

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The couple, who had decided not to learn the gender of their baby beforehand, announced the birth on their Instagram account, @SussexRoyal, with the words: “It’s a BOY!” , adding that they were “overjoyed”.

By the time Buckingham Palace announced just before 2pm that the Duchess of Sussex was in labour, she had already given birth hours before.

Harry later confirmed the news at a hastily arranged press conference. Speaking from Windsor, where they recently moved into their new home, Frogmore Cottage, Harry said: “I’m very excited to announce that Meghan and myself had a baby son this morning, a very healthy baby boy.

Facebook Twitter Pinterest The announcement on Instagram of the birth of the Duke and Duchess of Sussex’s first child. Photograph: @sussexroyal

“Mother and baby are doing incredibly well. It’s been the most amazing experience I could ever have possibly imagined. How any woman does what they do is beyond comprehension, but we’re both absolutely thrilled and so grateful to all the love and support from everybody out there. It’s been amazing, so we just wanted to share this with everybody.”

On a name, he said: “That’s the next bit … The baby is a little bit overdue, so we’ve had a little bit of time to think about it.” The couple planned to make another announcement on Wednesday “so everyone can see the baby”.

Describing what it was like to be present at the birth, Harry said: “This is definitely my first birth. It was amazing, absolutely incredible, and, as I said, I’m so incredibly proud of my wife.

Play Video 1:34 Prince Harry after Meghan gives birth to boy: ‘Absolutely over the moon’ – video

“As every father and parent will ever say, you know, your baby is absolutely amazing, but this little thing is absolutely to die for, so I’m just over the moon.”

Meghan’s mother, Doria Ragland, who flew in from her Los Angeles home for the birth of her first grandchild, is at Frogmore Cottage supporting her daughter. She was said to be “overjoyed by the arrival of her first grandchild”. The baby is a fourth grandchild for the Prince of Wales.

Meghan’s estranged father, retired lighting director Thomas Markle, was quoted by the Sun as saying: “I’m delighted to hear that mother and child are doing well. I am proud that my new grandson is born into the British royal family and I am sure that he will grow up to serve the crown and the people of Britain with grace, dignity, and honour.

“God bless the child and I wish him health and happiness, and my congratulations to my lovely daughter Duchess Meghan and Prince Harry, and God save the Queen.”

No details of where the duchess gave birth were released by Buckingham Palace, but the wording of the announcement fuelled speculation she had opted for a home birth at the couple’s newly renovated residence in Windsor. The place of birth is likely to be revealed on the official birth certificate.

In one unconfirmed report, the Daily Mail claimed Meghan’s hopes of having a home birth had been dashed and that the baby had been delivered at an exclusive central London hospital, possibly the Portland. The report claimed the couple had been driven to the hospital on Sunday afternoon, accompanied by Ragland, but returned to Frogmore Cottage within hours of the dawn birth.

Facebook Twitter Pinterest A combination of pictures shows the congratulatory banner message circling the BT Tower. Photograph: Daniel Sorabji/AFP/Getty Images

The Queen, Prince Philip, Prince Charles, the Duchess of Cornwall, the Duke and Duchess of Cambridge, and the late Diana, Princess of Wales’s siblings, Lady Jane Fellowes, Lady Sarah McCorquodale and Earl Spencer, had all been informed and were delighted with the news, Buckingham Palace said in a statement.

The Duke and Duchess of Cambridge were looking forward to meeting their new nephew, Kensington Palace said. An Instagram post on @KensingtonRoyal said: “The Duke and Duchess of Cambridge are delighted with the news of the birth of the Duke and Duchess of Sussex’s son today, and look forward to meeting the latest addition to the family.”

There were also congratulations from across the Atlantic, with Michelle Obama, the former first lady, tweeting: “Congratulations, Meghan and Harry! Barack and I are so thrilled for both of you and can’t wait to meet him.”

The baby’s title is expected to be the Earl of Dumbarton – as the son of a duke, he is entitled to use one of Harry’s lesser titles as a courtesy title – and his surname is expected to be Mountbatten-Windsor. He will will one day inherit the title of the Duke of Sussex from his father.

Speculation that the baby was overdue was fuelled on Friday when Harry, who has an official visit to The Hague scheduled for Thursday to launch the one-year countdown to the Invictus Games 2020, cancelled a visit to Amsterdam on Wednesday, which would have necessitated an overnight stay.

Facebook Twitter Pinterest Television crews work outside the Long Walk, Windsor Castle, following the news of the birth Photograph: Dominic Lipinski/PA

The couple announced in April that they had “taken a personal decision” to keep the plans around the arrival of their baby private. The wait had been a challenge for royal commentators faced with a paucity of facts beyond only that a royal birth was imminent.

The couple made clear there would be no hospital steps photocall with the newborn, as there was with William and Kate and their three children. It is understood the Sussexes thought there was no pressure for such a public show when the baby was not in the direct line of succession and unlikely to ever be monarch.

The first photographs of the baby could be released through the couple’s Instagram account. It is understood there will be a photocall with a small representative group of media in the coming days.

The new royal will not automatically be styled HRH or given the title prince or princess. That is the gift of the Queen, who will undoubtedly go along with the couple’s wishes. Princess Anne rejected royal titles for her two children, but both Prince Andrew’s daughters are princesses.

A framed notice of the birth has gone on display on a ceremonial easel on the forecourt of Buckingham Palace and will remain on display until 8pm on 7 May.

Facebook Twitter Pinterest Members of staff set up an official notice on an easel at the gates of Buckingham Palace. Photograph: Tolga Akmen/AFP/Getty Images

The arrival means Meghan will still be tending to the newborn when the US president, Donald Trump, makes his state visit to the UK on 3 June. Before marrying into the royal family, she was a vocal critic of Trump, previously calling him “divisive” and a “misogynist”.