The Princess of Wales has been a popular member of the royal family since marrying Prince William in 2011.
Kate was introduced to the royal family while dating William during their university years, including his father, King Charles.
In her engagement interview, she said: "I was quite nervous about meeting William's father, but no, he was very, very welcoming, very friendly, it couldn't have gone easier really for me."
And of William's late grandmother, Queen Elizabeth II, she recalled: "I first met the Queen at Peter [Phillips] and Autumn's wedding and again it was amongst a lot of other guests and she was very friendly."
Since then, Kate has forged close bonds with her father-in-law King Charles and stepmother-in-law Queen Camilla, as well as William's aunt, the Duchess of Edinburgh, and his cousin, Zara Tindall.
Ahead of Kate's 42nd birthday on 9 January, take a look at her best moments with her royal in-laws in the gallery below.
King Charles
Charles and his daughter-in-law share similar interests in art and environmental issues.
Just six months after her royal wedding, Charles asked Kate to host a private charity dinner at Clarence House on his behalf.
The pair appear to have a warm rapport with one another, with the King referring to Kate as his "beloved daughter-in-law" during his state visit to Kenya last November.
Queen Camilla and Queen Elizabeth II
In June 2021, Kate stepped out for a very rare joint engagement with the late Queen and the then-Duchess of Cornwall. Despite the formality of the event - the royals were attending the G7 summit in Cornwall - the ladies looked like they were having a wonderful time together.
The late monarch even joked about using a sword to cut a cake. When an aide pointed out that there was a knife, she quipped, "I know there is. This is something that is more unusual," prompting laughter from her relatives.
The Duchess of Edinburgh
Kate had good support from the likes of the Duchess of Edinburgh when she joined the royal fold.
The ladies are often seen chatting and laughing together at royal engagements and even hosted the Commonwealth Fashion Exchange at Buckingham Palace together in 2018.
Zara Tindall
At Royal Ascot in June 2019, Kate and her cousin-in-law Zara Tindall showed off their close bond as they hugged and kissed each other on the cheek. The royal ladies have a lot in common with their love of sport, fashion and have children of similar ages.
Mike Tindall
We love this hilarious exchange between Kate, Prince Louis and Mike Tindall from the Platinum Jubilee celebrations in 2022. The former rugby star gave a "I'm watching you" gesture to Louis as the young royal amused us all with his cheeky antics.
In an interview with Australian Woman's Weekly, published last month, Zara and Mike, who are also parents to Mia, nine, Lena, five, and Lucas, two, revealed that they often hang out with William and Kate and their brood.
"Our kids play with their kids in this competition we have," explained Mike.
Peter Phillips
Kate and William's cousin Peter share a giggle from the side lines as the Prince took part in a charity polo match in Windsor last summer.
Lady Louise Windsor
The Duke and Duchess of Edinburgh's daughter has had a special bond with Kate from a young age, as seen here at Trooping the Colour in 2012.
Lady Louise Windsor was one of William and Kate's bridesmaids at their royal wedding and has even followed in their footsteps by gaining a place at St Andrews University in Scotland.
The Princess Royal
Sharing a giggle with the King's sister, Princess Anne, during the RAF centenary celebrations in 2018. The royal ladies carried out their first joint engagement when they visited The Royal College of Midwives in May 2022.
The Duke of Edinburgh
A big hug from Kate for William's uncle, Prince Edward, at the Commonwealth Games 2022 in Birmingham.
The Waleses and the Edinburghs share a particular love of sport and were very animated together during the London 2012 Olympics.
Princess Eugenie
William's cousin Eugenie has been supportive of Kate's royal work and has attended every one of the Princess' Christmas carol concerts.
George and Charlotte were also chosen to be part of Eugenie's bridal party for her wedding to Jack Brooksbank in 2018.
