Instead, the royal was accompanied by a dark-haired lady, dressed in a dusty rose coat, who stood next to Charlene and her children.
Photos from the event make it clear that Charlene is very much at ease in her companion's presence – but who is her new right-hand lady. HELLO! takes a closer look…
Princess Charlene in conversation with Melanie-Antoinette Costello de Massy
She has been identified by Vanity Fair Spain as Melanie-Antoinette Costello de Massy, the daughter of Prince Albert's cousin, Baroness Elizabeth Ann de Massy. And the ladies certainly have an interesting relationship with the Monegasque royals.
Elizabeth's mother, Princess Antoinette, was the elder sister of Prince Rainier III – Albert's father.
Melanie-Antoinette Costello de Massy with Charlene and the royal twins
She had a long-term relationship with Alexandre-Athenase Noghes in the mid-1940s and together they welcomed three children: Elizabeth, Christian and Christine.
For some time, the siblings were excluded from the line of succession since they were born out of wedlock. That changed when Antoinette and Alexandre eventually did marry in 1951.
Princess Antoinette was Prince Rainier's elder sister
The marriage was not to last, however. Following the couple's divorce, Antoinette then began a relationship with Jean Charles Rey, president of the Monégasque parliament.
Together, according to Vanity Fair, the couple hatched a plan to dethrone Rainier, who was unmarried and had no children at the time.
Antoinette (far left) with Grace Kelly and Prince Rainier
They reportedly spread a rumour that his girlfriend, the French actress Gisèle Pascal, was unable to conceive. It's thought they hoped that a lack of heir would push parliament into recognising her son, Christian Louis, as next in line to the throne – and make Antoinette regent until he came of age.
The plan didn't work. Rainier went on to find lasting love with Grace Kelly, who he married in 1956, and together they had three children – Prince Albert and his sisters, Princess Caroline and Princess Stephanie. Relive the couple's magical royal nuptials here...
A look back at Prince Rainier and Grace Kelly's fairytale wedding
Prince Rainier passed away in April 2005 at the age of 81. At that point, Albert II acceded the throne – and Antoinette and her descendants lost their place in the line of succession to the Monegasque throne, which is limited to the current sovereign's descendants, siblings, and siblings' descendants.
Prince Albert with his father and his aunt
Any discord between Antoinette and Rainier didn't impact the rest of her family, however.
Rainier chose her daughter Elizabeth to be a bridesmaid at his wedding to Grace and also made her godmother to their daughter, Princess Stephanie.
Antoinette with daughter Elizabeth - bridesmaid at Rainier's wedding to Grace Kelly
Elizabeth also had a close bond with her cousin Albert; she represented him at various royal engagements and was photographed with him on a number of official outing.
Albert and Charlene with Baroness Elizabeth, Melanie-Antoinette's mother
Sadly, Elizabeth passed away in June 2020 at the age of 73. She died at the Princess Grace Hospital in Monaco and has been laid to rest in the Chapel of Peace.
She left behind her two children, Baron Jean-Leonard Taubert-Natta de Massy and daughter Melanie-Antoinette Costello de Massy.
Melanie-Antoinette and Prince Albert pictured together
And it seems she has passed her mantle on to Melanie-Antoinette who appears to have taken up the important role of supporting the royal family, namely Princess Charlene and her husband.
LISTEN: What Prince William and Kate are really like behind the scenes
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