From living together in a Chelsea flat in their 20s to sharing their motherhood journey with three children, Kate and her sister Pippa Middleton have always been incredibly close.

Pippa, 40, has been by her sister Kate’s side both in public and in private throughout their lives, and now lives just a stone’s throw away from the Princess’s home in Adelaide Cottage on the Windsor Estate.

And now more than ever, Kate, 42, who announced on Friday she’s been diagnosed with cancer, will be relying on her sister’s support after an ‘incredibly tough’ few months for her family.

Pippa was introduced to the world as Kate’s bridesmaid at her wedding to Prince William in 2011 as she carried her sister’s train up the steps to Westminster Abbey and even sparked romance rumours with her brother-in-law Prince Harry due to the giggles the pair shared on the day.

But after the royal wedding, Pippa has remained a rock for her sister, albeit while living a quieter life than the Princess of Wales – particularly since she moved to Berkshire with her husband James Matthews and their three children Arthur, Grace and Rose.

Pippa Middleton will no doubt be by Kate’s side during her recovery from cancer treatment as the pair share a very close relationship (pictured on Pippa’s wedding day in 2017)

In September, just ahead of Pippa’s 40th birthday, it was reported she and James had swapped their £17 million Chelsea residence for a quieter property in the county of Berkshire where she and her siblings spent much of their childhood.

As children, Kate and Pippa, who are less than two years apart in age, bonded over their shared love of exercise and sport. In particular, the pair were known to enjoy hockey, tennis and athletics while both pupils at Marlborough College.

The sisters’ mother Carole previously revealed a glimpse into the girls’ childhoods in an interview with the Telegraph.

Speaking in 2018, the owner of now defunct business Party Pieces revealed that, as s working mother, she instilled a strong work ethic in both Pippa and Kate, who were similarly focused on their studies at school.

The sisters have been incredibly close since childhood and were often spotted out and about in London in their 20s when they shared a flat in Chelsea

When they weren’t at school, Carole said the sisters ‘did a lot of modelling’ for Party Pieces, revealing: ‘Catherine was on the cover of one of the catalogues, blowing out candles. Later on, she did some styling and set up the First Birthday side of the business. Pippa did the blog. I still value their ideas and opinions.’

The sisters remained close when they reached university age and both chose to study in Scotland – Pippa at Edinburgh and Kate at St Andrews (after a brief stint in Edinburgh herself).

When they had completed their studies, the siblings moved down to the Big Smoke where they shared an apartment in Chelsea together.

During their early twenties while Kate worked for Jigsaw and Pippa moved into a PR and events career, the sisters frequented the London nightlife scene and were often pictured together visiting clubs beloved by high society in the noughties.

Although Pippa has previously been described as the more ‘outgoing’ of the two sisters, she remained a support to Kate during the Princess’s engagement to Prince William.

Shortly before the wedding, a source told the Daily Mail: ‘It’s all Kate, Kate, Kate for the moment, because [Pippa is] her closest ally and, genuinely, they are best friends. But even if they weren’t, Kate would struggle to trust anyone who wasn’t family.’

As they got older and big sister Kate married into the royal family, their nights out together turned into trips to sporting events like Wimbledon – where the pair have often been spotted in the Royal Box together.

And for a while, it seemed as if Pippa would turn her status as the future Queen’s younger sibling into a lucrative career.

In 2012, it was announced Pippa had landed a book deal from Penguin worth £400,000 for a party planning tome.

In the foreword to her party planning guide Celebrate Pippa wrote: ‘It’s a bit startling to achieve global recognition before the age of 30 on account of your sister, your brother-in-law and your bottom. One day I might be able to make sense of this.

‘I certainly have opportunities many can only dream of. But in most ways I’m a typical girl in her twenties trying to forge a career and represent herself in what can sometimes seem rather strange circumstances.’

However, reaction to her party planning book, Celebrate, was grim. There was a critical panning and and sales were poor.

That same year, Pippa became a regular columnist for several publications, and contributed several articles to The Spectator magazine, and it was reported that NBC would offer Pippa $600,000 to be a royal correspondent but this was denied by the network.

She started having a food column in the supermarket magazine Waitrose Kitchen beginning in spring 2013.

At the time, it was said that ‘Pippa’s Friday Night Feasts’ would advise on the best meals to start the weekend off with friends.

Pippa and Kate, both avid tennis fans, have been spotted in the Royal Box at Wimbledon numerous times over the years

In 2019, Kate and Pippa were sat in the Royal Box with Kate’s sister-in-law, the Duchess of Sus𝓈ℯ𝓍

In June 2013 she was named a contributing editor of Vanity Fair and wrote a series of columns for the magazine.

Pippa also began started writing a fortnightly sports and social column for The Sunday Telegraph that September.

And in 2014, according to the Daily News, the freelance columnist hoped for a deal ‘upward of $500,000’ to report on lifestyle and health issues for NBC.

Pippa was in talks with the ‘peacock network’ for a new job after she was interviewed by Matt Lauer, and the network was reportedly in serious talks with Pippa for months about becoming a lifestyle and health correspondent.

However the deal never materialised and, within months, Pippa also parted ways with The Telegraph.

Meanwhile her last columns for the Spectator and Vanity Fair magazines were published in 2015.

Now, she’s seemingly left all thoughts of being a lifesyle influencer and writer behind and is running the Bucklebury Gift and Farm Shop set deep in the Berkshire countryside, near to Pippa’s £15 million country home.

Pippa bought the 77-acre site with husband James Matthews in 2020 and hopes to turn it into thriving commercial enterprise.

The farm project – dubbed Pippa’s Playground – already has a petting zoo, a cafe and cabin accommodation for 30 guests, as well as hosting birthday parties with tractor rides.

Although Kate’s life has changed significantly since she married Prince William, Pippa has previously revealed their sisterly relationship hasn’t been affected by the Princess of Wales’s role as a senior royal.

Speaking to Today in the US in 2014, Pippa said she and Kate ‘spend a lot of time together’ despite the ‘pressures’ her sister faces in her public role.

Pippa added: ‘We still do a lot together as a family and I think that’s really the heart for all of us is having a really close family that we can sort of be normal with each other, treat each other normally. And that’s sort of kept us all, you know, affixed to the ground.’

The second Middleton sibling also revealed she is able to call Kate any time she wants a little bit of ‘girl talk’ and that the pair have a ‘normal, sisterly relationship’.

Pippa famously stole the spotlight during the Royal Wedding in 2011 when she donned a curve-hugging white bridesmaid’s gown for the ceremony

(L-R) Carole Middleton, Michael Middleton and Pippa Matthews leave after attending the ‘Together at Christmas’ community carol service at Westminster Abbey on, 8 December 2021

Kate Middleton (R), her mother Carole Middleton and sister Pippa Middleton arrive at The Goring Hotel after visiting Westminster Abbey on April 28, 2011

She said: ‘We’re very close. And, you know, we support each other and get each other’s opinions and things.’

After Pippa shot to fame in her Alexander McQueen bridesmaid dress at William and Kate’s royal wedding in 2011 which was watched by millions around the world and hosted at Westminster Abbey, the younger Middleton sister again played down the significance of the event, proving that Kate’s royal status does not faze her, nor does it affect their relationship.

She told NBC: ‘It sounds funny to say, but we saw it as just a family wedding. And actually, I didn’t realise, perhaps, the scale of it until afterwards. We all took on the roles as any family would.’

As Kate has stepped up her role as a senior working royal in recent years, Pippa has remained supportive of her older sister, including accompanying her on a tense outing to Wimbledon with Meghan Markle in 2019.

In the months prior to the joint engagement, rumours had started to circulate of tensions between the two royal wives and the Wimbledon day out was a high profile opportunity to put them to bed.

So it’s no wonder that Kate invited her sister along for support on the much-scrutinised occasion.

Pippa sat alongside Meghan in the Royal Box and was seen laughing and joking with Prince Harry’s wife to keep the mood light.

She has attended the Princess’s Carol Concert in Westminster Abbey every year since Kate has been hosting the event – and even took part in a display of solidarity at the concert two years ago.

In December 2022, when the date of the Christmas event fell on the same day that Harry and Meghan’s explosive Netflix series landed, Pippa was one of many women in Kate’s inner circle to rally around the Princess as they all arrived at Westminster Abbey wearing the same coloured outfits – a shade of burgundy.

It’s likely that the outfits were planned in advance of the Netflix series, however the image of solidarity was striking amid explosive accusations levelled at Kate and William by the Sus𝓈ℯ𝓍es.

Now, as Kate announces to the world she has been diagnosed with cancer, she will no doubt be leaning on her sister more than ever.

A source told the Times: ‘The three siblings are incredibly tight … Pippa not only as a sister but as a best friend she can confide in. They are extremely loyal to one another.’

The newspaper noted the pair had shared a trip to the ski resort of Meribel with their husbands and children last winter – something that had been kept out of the public eye.

Royal insiders have told the Daily Mail that the family will ‘come back stronger’ from the shock of both the King and the Princess being diagnosed with cancer.

And, with her loyal and loving sister by her side, royal fans can rest easy knowing she has the very best support from a strong unit.