Princess Kate and Prince William’s motivation for sending a public birthday message from their social media account to Prince Harry has been revealed by a palace insider. The Duke of Sussex received public birthday wishes from King Charles’s Royal Family account and Kate and William’s account on X, formerly known as Twitter. The Royal Family account posted at 8:28am on Sunday morning: “Wishing The Duke of Sussex a very happy 40th birthday today!” The post was accompanied by an image of Prince Harry smiling. Just over two hours after the Royal Family message, a similar one was posted on the Pri…