Along with The King and Queen Camilla, Prince William and Princess Kate, who share a close bond with the Edinburghs, are said to be joining the festivities. The Princess of Wales and Duchess of Edinburgh are said to have a particularly strong relationship, with Kate viewing Sophie as a sort of "royal sister."

Kate Middleton found a mentor in Sophie, the Duchess of Edinburgh when she was first welcomed into the royal fold, but their warm working relationship has developed into an even closer sisterly bond amid Kate’s cancer battle.

Princess Kate and Prince William have shown unprecedented openness about their relationship following Catherine's cancer journey, according to sources close to the royal household. A source told People magazine that the Prince and Princess of Wales are "more open" now and "talk about their relationship together.

Kate Middleton's fashion choices have regularly inspired shoppers to purchase whatever she's wearing. And according to a new report, the Princess of Wales might soon be able to give brands in areas other than fashion her royal seal of approval.