Today will see a royal first when the Duchess of Cambridge teams up with Princess Anne for a rare joint engagement.
The pair will take part in a joint visit to medical colleges working in the areas of maternal healthcare.
Anne is patron of the Royal College of Midwives (RCM) while Kate is patron of the Royal College of Obstetricians and Gynaecologists (RCOG), and the royal women will visit their headquarters in London.
Both women are one of very few current senior working royals - and are usually only photographed together at family events such as Christmas at Sandringham or Trooping the Colour.
But despite seemingly appearing at ease in each other's company, how close are the pair? Here we take a look...
'Difficult' royal pressure
Anne, 71, is the aunt of Kate's husband Prince William - so it's likely that Anne and Kate, 40, have spent a lot of time together during big Royal Family get togethers.
However, when it comes to their official royal duties - their paths very rarely cross.
Although that is not to say Anne does not appear to take an interest into what Kate has been up to and the media attention surrounding her.
And speaking in a documentary, the Queen's daughter did reveal her sympathy for younger royals, who have entered the royal stage in the social media era - such as Kate
She told the ITV film Anne: The Princess Royal at 70: ""The pressure that is applied to the younger members of the family, it's always worse.
"That's what the media is interested in. That's hard sometimes to deal with. But there was no social media in my day, and it's probably made it more difficult."
Love of sports
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Kate and Anne's seeming ease with each other may be down to one love they both appear to share - sport.
Kate is well-known for her sporty nature, and has played football, rugby, cricket and hockey on several engagements in the past.
Meanwhile, Anne is also known for her love of sports - and in 1971 became the first member of the Royal Family to compete in the Olympics.
So it's no surprise that the pair were spotted together at the London 2012 Olympics together enjoying one of the sailing events.
However, when it comes to sport, the women may have a slight rivalry with rugby - Kate is patron of the English Rugby Union while Anne has the same job, but with the Scottish Rugby Union.
Surprise remark
But despite their shared interests and jolly bond, there were some eyebrows raised by a comment made by Anne when Kate announced her pregnancy with oldest child Prince George.
According to the Express, when Anne was asked about the upcoming addition to the Royal Family in 2013, she reportedly responded: “Nothing to do with me, but it’s very good news.”
Royal fans responded on Twitter, calling the Princess Royal “miserable”.
One said “strange comment, don’t understand her” while another wrote: “How rude and disrespectful!!!”
Working more closely
Today will see Kate and Anne make a rare official appearance together - so will there likely be more in the future?
Royal expert Richard Fitzwilliam told the Express: "It's a very good idea because this is maximising the potential of members of the Royal Family who are popular and hard working.
"This dream team pairing, it's been called, I think this is a really good idea and I'm sure that it will happen again."
While the Mirror's royal editor Russell Myers recently told the Pod Save the Queen podcast: "I have been saying this for a quite a while, that there would be a lot more collaboration between them because, well there not only has to be, but I think in the wake of the Sussexes leaving, they really did want to batten down the hatches and help each other — especially after coronavirus and it was really from the very top.
“The Queen was saying: You do really need to work together, that is what the monarchy is about — helping each other to present and publicise your causes, because that is the only way that they are going to survive.”
