Lady Sarah Spencer, as she was known before her marriage to Neil McCorquodale, dated Prince Charles briefly and was the one who introduced him to her younger sister.
She and her family reside near Grantham, Lincolnshire, and she has largely stayed out of the public eye since her sister Diana's tragic death in 1997.
WATCH: Princess Diana and Prince Charles leave St Paul's Cathedral after their wedding
Lady Jane Fellowes at Harry and Meghan's wedding
Lady Jane, who is married to the Queen's former private secretary, Robert Fellowes, gave a reading of the Song of Solomon at Harry and Meghan's wedding in 2018, and was chosen by the Duke and Duchess of Cambridge to be godmother to Princess Charlotte.
William and Harry also share a close bond with their cousins too. Lady Sarah has three children, Emily, George and Celia McCorquodale, while Lady Jane is mother to Laura, Alexander and Eleanor Fellowes.
Lady Sarah McCorquodale at the royal wedding in 2018
Over the years the royal brothers and their cousins have attended one another's weddings, with Harry and Meghan celebrating the nuptials of Celia McCorquodale and George Woodhouse just a month after their own marriage.
The Sussexes also made sure that Diana's sister and younger brother, Earl Spencer, were included in the official statement announcing the birth of their firstborn Archie in 2019.
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