The seven-day visit is their daughter's first overseas trip
Britain's Prince William and his wife Kate have arrived in Canada for their second official visit - but this time as a family of four.
The seven-day visit is their daughter Princess Charlotte's first overseas tour and only the second official foreign trip for their son Prince George.
The family landed at a military airport in Victoria, the capital of British Columbia, where they were welcomed by Canadian Prime Minister Justin Trudeau.
William and Kate first visited Canada, the largest Commonwealth country, in 2011 shortly after they got married.
But this time the couple are visiting a different part of the country with engagements across British Columbia and Yukon.
Speaking ahead of the visit, a Buckingham Palace spokesman said: "They are incredibly grateful to Prime Minister Justin Trudeau for the invitation to visit Canada.
"This visit is a chance for the Duke and Duchess to deepen their relationship with a country that they will visit many times over the course of their lives."
Talking about the decision to bring the children, the spokesman added: "They have received so many wonderful messages from Canadians since the birth of their children and look forward to having the chance to introduce their young family to the country."
The couple have previously hinted they were keen to take three-year-old George and one-and-a-half-year-old Charlotte to as many Commonwealth regions as possible before they start school.
The couple and their children will be staying at Government House for majority of the visit.
The tour will take them from the city of Vancouver out to some of Canada's more remote communities including Bella Bella, Whitehorse and the island of Haida Gwaii.
They will visit Great Bear rainforest, experience First Nations culture and meet Syrian refugees who have recently arrived in Canada.
Prince George and Princess Charlotte will be looked after by their nanny at Government House in Victoria, and are expected to be seen publicly just three times during the tour.
Prime Minister Trudeau said ahead of the family's arrival: "Canadians have tremendous affection for the Royal Family, and are excited to welcome the Duke and Duchess to our nation for their second official Royal Tour of Canada.
"Sophie and I look forward to showcasing beautiful British Columbia and to promoting awareness of both youth and mental health issues alongside Their Royal Highnesses."
Speaking at the welcome event outside the British Columbia Parliament buildings, Prince William said: "Catherine and I are delighted to be back in Canada.
"When we were here last time, we had been married only three months.
"The warm welcome that you gave us at that important moment in our lives meant a lot to us - and we have never forgotten it."
He added: "That is why we are so pleased that George and Charlotte can be with us in Canada this time round, beginning their own lifetime of friendship with this wonderful country.
"Over the next week, Catherine and I will see once again what makes Canada such a special place in the world."
New research carried out by Ipsos to coincide with the royal tour found that 58% of Canadians believe the constitutional monarchy helps to define Canada's identity, with 70% thinking that William and Kate will help to keep the monarchy relevant to Canadians.
But some have complained that Canada has to foot the bill for the tour, as it is a Commonwealth country.
Republicans also want a full parliamentary debate on the role of the British Queen as head of state.