"It's about time," he joked.
"I can't wait to be an uncle."
A natural with children, Harry has often demonstrated his ability to connect with youngsters.
He is patron of WellChild, which is dedicated to the needs of sick children and their families and whose nurses provide specialist medical care and direct support in the homes of chronically ill youngsters.
His own charity Sentebale helps vulnerable children in the southern African country of Lesotho.
Add to his caring side his cheery outlook, love of sports and capacity for fun and Harry will be well placed to entertain the new royal infant.
Roger Olley, of Including Men, an organisation promoting male inclusion, said: "Uncles are immensely important and the emerging research on this is particularly strong in America with black boys.
"Uncles offer a different type of parenting that isn't constrained and constricted by family norms.
"The uncle can take the child out of that environment and offer them a different experience in a safe way. They can widen the child's experiences."
He urged uncles such as Prince Harry to be "confident in their maleness".
"I would say to any father or man, be confident in your maleness and confident in the different things you have to offer. It's a political hot potato but that's what it's about," he said.
Mr Olley added that research had shown that involvement of male figures in family life helped with development of more complex language and different styles of play, with male play often being more physical.
He warned that the importance of uncles and men in general in childhood development was often overlooked.
"It's an under-recognised role - very, very much so," he said.
When best man at William's wedding, Harry reportedly bought a wiggly worm toy for the Duchess of Cornwall's three-year-old granddaughter Eliza Lopes, who was a bridesmaid.
When she became scared of the roaring crowds in the carriage ride back to Buckingham Palace, he gave it to her to make her laugh.
The Prince, who was once photographed playing strip billiards in Las Vegas, is already a godfather to former nanny Tiggy Legge-Bourke's eldest son Fred, attending his end of term school play last year.
In December 2012, a survey by Cupid.com found that 85 per cent of men and 98 per cent of women questioned thought Harry would make a "cool uncle".
- PAA
