The former President and First Lady have a longstanding relationship with Harry, 36, after they bonded over the Prince's hugely successful Invictus Games initiative. They famously starred in a video montage with Harry and the Queen to promote the 2016 competition, and the duke subsequently interviewed the former commander-in-chief on Radio 4. When Michelle gave a talk at London's Southbank Centre in December 2018, Meghan made a point of attending – and the two women were said to have had a long "power meeting" backstage, during which they discussed their shared passion for girls' education.
And, despite the Obamas having not attended the Sussexes' wedding that year, it was thought that the newly California-based couple would be shoo-ins at Obama's 60th, as prominent "progressives" and new-found members of the influential US metropolitan liberal elite.
Meghan's close friend, the CBS news anchor Gayle King, had made the cut after all and although she did not attend, Oprah Winfrey is also believed to have been asked to save the date.
So why weren't the duke and duchess on the dancefloor? Could this be a sign that the Sussexes' love affair with the Obamas has gone cold?
Confusion surrounds whether they were snubbed or simply couldn't make it after the website Page Six, which broke the news of Harry's multi-million pound book deal, reported that they were "not planning to attend" the shindig.
Having welcomed their second child, Lilibet, into the world in June, the couple are currently on parental leave – although Meghan did manage to record a video with actress Melissa McCarthy last Wednesday to mark her 40th birthday.
Although Obama turned 60 on the same day – August 4 – neither he nor Michelle were seemingly invited to participate in Meghan's new charity initiative to donate 40 minutes of time to mentoring women returning to the workplace after Covid.
Celebrities who were asked to support the 40x40 drive included Hillary Clinton, singer Adele and fashion designer Stella McCartney. Yet with some criticising the scheme as "self-serving" and "woke", could the Obamas be fearful that their ongoing association with the royal couple risks attracting negative publicity?
Some in Democratic circles have suggested that the Sussexes' attempts to ape everything the Obamas have done since they left the White House could have jeopardised their once "special relationship".
After leaving the royal family and moving to Montecito near Santa Barbara in March last year, Harry and Meghan appear to have used the Obamas' modus operandi as a blueprint for their own Stateside relaunch.
Like them, they have signed a lucrative multi-million dollar deal with Netflix to produce their own documentary series, while Harry last month announced he is writing his memoirs for Penguin Random House, which is the former President's publishers. His autobiography, A Promised Land, was released in November 2020, two years after Michelle published her own life story, Becoming.
Intriguingly, the Obamas had a similar format to Meghan's 40x40 initiative to personalise the weekend's birthday party, emblazoning everything with a bespoke 44x60 logo to symbolise the 44th President's 60th birthday.
There is also the issue of the Obamas' loyalty to the Queen. When the couple paid a state visit to Britain in 2011, they got on famously with the monarch and her family. The only president to be offered a full state visit since George W Bush in 2003, photographs of the three-day extravaganza, which featured a lavish state banquet, showed the Obamas, the Queen and the late Duke of Edinburgh relaxed in each others' company, and in a show of mutual respect.
So intimate was the meeting that Prince Philip, then 94, turned chauffeur to drive the Obamas to lunch at Windsor Castle in his navy blue Range Rover.
The foursome had first met during the G20 summit in 2009, when Michelle was famously photographed putting her arm around the Queen, who responded by placing a hand on the former First Lady's waist. In her memoir, she explained that she had not been aware of "royal protocol" and had simply reacted after the two women had agreed that a long day wearing heels had left them with sore feet.
We were just "two tired ladies oppressed by our shoes", she wrote.
The incident certainly did not cause any friction with the sovereign, who a few years later when they visited London privately, gave Michelle and her daughters Malia and Sasha a guided tour of Buckingham Palace.
Describing how much she liked the Queen during her 2019 book tour, Michelle said: "She's wonderfully warm. And funny. And she's elegant and kind and considerate in really interesting ways. That kind of warmth and graciousness, and intelligence and wit. I like her."
After the Duke of Edinburgh died at the age of 99 in April, Obama's tribute was among the most heartfelt.
So it arguably will not have gone down particularly well with a couple that have always put "family first" to see Harry and Meghan being so openly critical of their royal relatives during their Oprah interview in March. During the 90-minute prime time tell-all, the couple accused the monarchy of failing to support them and suggested that Prince Charles and Prince William were "trapped" in The Firm. It is perhaps worth noting that the Obamas are also close to the Duke and Duchess of Cambridge, who were central to the 2011 state visit, which took place just weeks after their wedding.
When the Obamas returned to the UK in 2016, they made a point of popping into Kensington Palace, when they were introduced to a then 3-year-old Prince George, ready for bed in his dressing gown, before sitting down to dinner with William, Kate and Harry. Last October, the former President made a point of supporting William's newly launched Earthshot Prize, tweeting: "It's going to take a lot of big-thinking and innovation to save the one planet we've got – and that's why @KensingtonRoyal's leadership on climate change can make a real difference."
"The Obamas didn't like Harry attacking his family. They value family and certainly aren't the type of people who would want their children talking to the press," says one insider.
But perhaps the greatest clue to the Obamas' feelings was given by Michelle when she was asked to respond to the Duke and Duchess of Sussex's recent outpourings on Oprah. "I just pray that there is forgiveness and there is clarity and love and resolve at some point in time because there's nothing more important than family," she said.
It seems that when it comes to Harry and Meghan, the former President and First Lady remain firmly of the view that blood is thicker than water.
