Royal author Andrew Lownie shared his take on what went wrong between the sisters-in-law ...

Princess Diana and Sarah Ferguson were fourth cousins and childhood friends before they became sisters-in-law by marrying into the royal family.

The Princess of Wales told her school friend that it was "wonderful being married" two months after her wedding to the future ...

Diana reportedly penned a letter to former classmate Katherine Hanbury, sharing intimate details of her wedding.

The socialite had fans seeing déjà vu.