Cradling his son, wrapped in a white blanket and wearing a hat, Harry and Meghan appeared before a small group of media at St George's Hall in Windsor castle where they held their wedding reception just under a year ago.

Britain's Prince Harry and Meghan, Duchess of Sussex are seen with their baby son, who was born on Monday morning, during a photocall in St George's Hall at Windsor Castle, in Berkshire, Britain, on May 8, 2019. (Pool via REUTERS/Dominic Lipinski)

"It's magic - it's pretty amazing and I have the two best guys in the world so I am really happy," Meghan said when asked how she was finding being a new mother.

She said the boy, the seventh-in-line to the British throne who has not yet been publicly named, had the sweetest temperament and was sleeping well.

"He's just been a dream so it's been a special couple of days."

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The baby was born in the early hours of Monday morning, weighing 7 lb 3oz (3.26 kg), but few other details have been given about the birth.

"It's great, parenting is amazing," Harry said. "It's only been two-and-a-half days, three days, but we're just so thrilled to have our own little bundle of joy, to be able to spend some precious time with him as he slowly starts to grow up."

The couple said they were about to visit 93-year-old Elizabeth, the world's longest-reigning monarch, at the castle to allow her to meet her eighth great-grandchild.

Meghan's mother Doria Ragland is staying with the couple at their home Frogmore Cottage, on the castle's estate.

"It will a nice moment to introduce the baby to more family and my mum's with us as well," Meghan said.