James, Arthur among the contenders in the name guessing game for Britain's new royal baby

The baby boy is expected to be given three names, an expert says.

“You’ll find out soon enough,” William, 35, said to well-wishers gathered outside St. Mary’s Hospital in London Monday.

Royal watchers are not waiting for William and Kate to make a name announcement, instead placing their bets on names with royal significance.

“In terms of middle names, I think Philip is an absolute pretty rock hard certainty, if there is such a thing,” ABC News royal contributor Imogen Lloyd Webber told “GMA.” “Philip would be a lovely tribute to William’s grandfather.”

One of the names leading the speculation among royal watchers is James, the name of Kate’s brother, James Middleton.

Charlotte is Middleton’s middle name, and it is also the feminine version of Charles, William’s father’s name.

In addition to James, the names Arthur, Albert, Philip and Henry are some of the most talked about contenders for the royal baby’s name.

In 2013, the baby’s older brother, Prince George, was named after Queen Elizabeth’s beloved father, King George, who died when the queen was 26 years old.

William and Kate revealed George’s name -- George Alexander Louis – two days after his July 22, 2013, birth.

The new baby, who weighed 8 pounds, 7 ounces at birth, is now fifth in line to the throne behind Prince Charles, William, George and Charlotte.

His official title will be His Royal Highness Prince [TBD Name] of Cambridge.