LONDON -- Boy or Girl? Even the Duke and Duchess of Cambridge are professing they will be as surprised as the rest of us.

An aide to Prince William and the former Kate Middleton says Prince George is eagerly awaiting a new brother or sister later this month, though they say they don't know which it will be.

At a briefing Thursday, aides said the couple are grateful to people around the world who have wished them well. They noted with understatement they are aware the media is watching.

The royal couple hope the birth will be covered "in a celebratory and dignified manner," an aide said, speaking on condition of anonymity customary for briefings.

Before the world is told, Queen Elizabeth II will be informed.