The Family Order is the personal gift from the Sovereign to female members of the family. Princesses of the Blood used to receive it automatically, but wives of Princes of the Blood Royal have to earn it. The Princess of Wales received the Order within the first few months of the her marriage to the Prince of Wales in 1981. The Duchess of Cornwall, Countess of Wessex, the Duchess of Kent and Gloucester are also recipients of the Order.
I have been told by a very reliable authority that Princesses Beatrice and Eugenie have not received the Royal Family Order.
The Duchess of York did not receive the Order during her marriage to the Duke of York.
Princess Michael of Kent has not received the Order. She has been married to Prince Michael since June 1978.
The Duke and Duchess of Cambridge were given the highest precedence after the Queen and Prince Philip. Duke of Edinburgh, taking the positions of the Prince of Wales and the Duchess of Cornwall.
No announcement is made when the Queen bestows this gift. Perhaps the Queen is waiting for Catherine to realize that it is time to be a full time royal, and start taking on new patronages, and other duties. When Lady Alice Montagu-Douglas-Scott married the Duke of Gloucester in November 1935, she acknowledged that marrying into the Royal Family meant she would become a servant of the country.
At some point in the not-too-distant future, Catherine will wake to find that she is the Duchess of Cornwall and Cambridge, the wife of the heir apparent. (Prince of Wales is not a hereditary title, but reserved for the heir apparent. It will be up to Charles III to bestow the titles Prince of Wales and Earl of Chester on William.) At that time, she will have run out of excuses because the wife of the heir to the throne is a full time position. No ifs. ands, or buts about it.