And while Prince Williams and Duchess of Cambridge, whose maiden name is Kate Middleton, have made no official comment about the baby due in mid-July, Harry has found it hard to keep the secret, reports mirror.co.uk.
"Harry has been telling everyone Wills (Williams) and Kate are having a boy and how thrilled he is at the prospect of having a little nephew," said a source.
The source added: "He said the whole family were excited about it. Apparently, Kate has always wanted a boy. The close inner circle all know that it's a boy and they're busily buying gifts with a boy theme."
The British couple is not sharing information about the baby.
The source further added: "They're really working hard on baby names now and think they have it sorted. But they won't reveal anything to anyone - not even Harry. Of course, Harry's been making up crazy suggestions and winding them up too."