They even turned down an invitation from their friends last week in favour of their holiday with the Middletons.
Holly Branson, daughter of Sir Richard, had invited them to join her, Princess Beatrice and her boyfriend Dave Clark at a party at the Branson family chalet in Verbier, Switzerland.
A source said: "They were invited to join Holly and her friends on the slopes but William and Kate chose to go away with her parents instead. Their friends see a lot less of William and Kate these days."
Indeed, the Duke and Duchess of Cambridge have holidayed with the Middletons before, going to Mustique together earlier this year.
The couple have vowed to holiday with Kate's parents at least once a year, as William enjoys a warm rapport with both Carole and Michael, whom he sometimes jokingly refers to as Dad.
But at a recent shooting party, Harry was bemoaning his brother's quieter new life. He was joking that "William has become rather boring and has stopped going out since he got married", says the source.
William doesn't really go out any more, and Kate never did. They are both just happy at home eating home-cooked suppers, curled up on the sofa watching movies.
Next week, the couple will return to Anglesey for more of that ordinary life as Mr and Mrs Wales, as they like to be known.
William will report for his search-and-rescue shifts at RAF Valley as usual, while Kate will be settling back into domesticity.
To make the most of this life, William has insisted that his and Kate's diaries are cleared of royal engagements for the coming months.
He is especially keen that his wife, who has been thrust into the spotlight in his absence, should have some time to herself. A courtier confirmed: You will not be seeing the Duchess now for some time.
While her husband was away, Kate delivered her first public speech at a children's hospice in Ipswich later admitting she had been wracked with nerves. She was said to be shaking like a leaf at the event last month.
The Duchess has apparently jokingly said that the stress of recent weeks is causing her to turn grey and indeed, she revealed the merest hint of silver hair beneath her jaunty Lock and Co headwear on a recent public engagement.
Kate, who visits the Richard Ward salon in Sloane Square every six weeks for a trim and colour, saw her colourist before William's homecoming, but she has been so busy lately that her regular grooming sessions have fallen by the wayside.
Not that such cosmopolitan trappings are important to a couple who prefer to live life below the radar in their five-bedroom cottage in rural Anglesey.
They love to walk and dine alfresco, often using the sausage maker Kate bought William two summers ago. They enjoy DVD box sets, and Kate has the latest series of acclaimed Danish crime drama The Killing lined up for their next sofa session.
They do not have staff in Wales. Instead, Kate does the cooking, stocking up on supplies at the local branch of Waitrose.
Friends of the couple say they both joke about getting old together but their current quiet life is, inevitably, only a temporary one.
When the couple married, the Queen agreed to give them a two-year grace period, but by next year the couple will move into the late Princess Margaret's home at Kensington Palace, where they will raise their family.
William will then have to decide whether to stay in the RAF or embark on a life of Royal duty. The decision will not be his alone, and the Prince, aware that his destiny is already mapped out, has described this as borrowed time.
But the couple are determined to make the most of it even at the risk of jokes about their premature middle-age.
William's balding pate is always the butt of Harry's jibes especially while the younger brother continues to lead a busy social life as part of the Brompton Set, a clique of well-heeled young professionals who dine at the Markham Inn on Chelsea Green and drink at the private Brompton Club.
In contrast, while at their London base, Nottingham Cottage within Kensington Palace William and Kate keep a lower profile.
Their only excitement is playing tennis together at the Harbour Club in Chelsea, where Kate has been taking lessons from a coach.
They are fiercely competitive on the court, which is one of the few times they do occasionally bicker, but Kate is determined to maintain her game, which is stronger than William's.
It is one more small piece of normality the couple will be keen to hold on to as long as they can.
- DAILY MAIL
