Inside Prince Albert's Relationship With His Cousin, Melanie-Antoinette Costello De Massy

Prince Albert of Monaco has been known to seriously rely on the women in his life — and, no, we aren't referring to his heyday as the "playboy prince." Ever since Albert took the Monegasque throne in 2005, he has required a number of highly-ranked individuals to advise and support him. Chief among these counselors have been his sisters, Princess Caroline and Princess Stéphanie, who have long propped up the prince.

And, so far, despite their own personal scandals, their efforts have been successful. While Stéphanie agreed to become the godmother of Albert's illegitimate son, Alexandre Grimaldi, Caroline has helped the prince choose who to trust. Speaking to People about the matter, Albert shared, "Every time I've asked [Caroline] about this or that situation or about this person I'm not sure of, she's demonstrated very good judgment."

That being said, there have been times when Albert has required the assistance of a more low-profile family member — someone who does not share Caroline or Stéphanie's history of improper behavior. The prince can count on his second cousin, Mélanie-Antoinette Costello de Massy, to help the royal family without stepping into the limelight. Over the years, Mélanie-Antoinette has silently provided Albert with her assistance, accompanying him to royal events and even occasionally stepping in for him when he has been indisposed. And, ever since Princess Charlene fell ill with an infection in 2021, Mélanie-Antoinette has taken on an even bigger role.

These days, Prince Albert and Mélanie-Antoinette Costello de Massy are fast friends, but that wasn't always the way things were between their two families. A generation ago, Mélanie's maternal grandmother, Princess Antoinette, tried to steal the throne from Albert's father, Prince Rainier. 

At the time, there was a little bit of drama over who would inherit the crown. As Hello Monaco noted, this was because the previous ruler, Prince Louis II, had left no legitimate heirs... but he had conceived a daughter named Charlotte with his longtime mistress. Thus, Louis named the young woman Hereditary Princess Charlotte — a controversial political move that allowed his two illegitimate grandchildren, Rainier and Antoinette, to enter the line of succession. 

Interestingly, in Monaco, male heirs are prioritized over female ones in the line of succession. As explained in Vanity Fair France, this meant that, even though Rainier was younger than Antoinette, he would become the crown prince, while she would remain in a more symbolic princess position. Perhaps due to a bit of sibling rivalry, Antoinette did not like this arrangement one bit. Thus, the princess took advantage of the confusion already clouding the issue of inheritance and began to spread rumors about her younger brother. Antoinette started to tell people that Rainier would not make a good prince because his long-time girlfriend, Gisèle Pascal, was unable to have children — or a legitimate heir. Ultimately, the princess' plan failed, and Rainier ascended the throne.

Of course, though, Prince Albert and Mélanie-Antoinette Costello de Massy have a professional relationship in addition to their cousinly bond. The two are believed to spend a great deal of time strategizing about the future of the royal family. Mélanie-Antoinette has been spotted supporting Albert during key moments — chief among these, the period of 2021 when Princess Charlene left Monaco due to a mysterious illness.

As the Daily Mail reported, Charlene spent very little time in the principality, choosing instead to heal in South Africa and later Switzerland. Unfortunately, the princess' absence sparked all sorts of rumors, with some people saying that royal life was too challenging for Charlene. Others yet whispered that Albert and his wife were thinking of getting a divorce, rumors which the palace firmly denied. Regardless of whether or not this gossip was true, however, the princess' absence meant that Albert would have to go to royal engagements alone. And, this was not great for the royal family's public image.

Luckily, Mélanie-Antoinette did not hesitate to take over for Charlene during the time that the princess was gone. She not only performed her own royal duties, but also performed many of Charlene's as well — attending event after event on Albert's arm. In July 2023, Mélanie-Antoinette accompanied the prince to Wimbledon, where she made sure that Albert never sat alone. She also maintained a low profile, giving him the spotlight. 

At the end of the day, Mélanie-Antoinette Costello de Massy is to Monaco what Sophie, Duchess of Edinburgh is to Great Britain. Like her English counterpart, Mélanie-Antoinette understands her position in the royal hierarchy and does not seek out a grander role. She avoids giving controversial interviews, behaves in a proper way, and lends her services to the crown out of loyalty and nothing more. 

As one royal insider put it to Point de Vue, Mélanie-Antoinette "has taken over the Country-Club and the Tennis Open as well as the Canine Society and dog show. She seems in particular very committed to the Country-Club. She is intelligent and will know ... her place, probably better than her half-brother Jean-Léonard."

All in all, Mélanie-Antoinette seems to bring a sense of consistency to the table — something Albert almost certainly appreciates. Between Princess Caroline's moving to France to Princess Stéphanie's stint with the circus, his sisters haven't always been the most present. (That said, they have certainly stuck to many of their royal duties.) And, of course, there are all the rumors about the state of Albert and Princess Charlene's relationship that may lead one to assume they aren't exactly on the same page.