The young royal family has arrived at Balmoral Castle in Scotland to be by Elizabeth's side
Credit: Chris Jackson/Getty

When Queen Elizabeth arrived at Balmoral Castle on Wednesday afternoon after her outing to open a new rail line on her record-breaking day, she kicked back with two future kings.

Prince William and Princess Kate – and their children Prince George and Princess Charlotte – have joined her at Balmoral, PEOPLE confirms. It is believed they arrived late Tuesday. (And it is 4-month-old Charlotte’s inaugural trip there!)

The young royal family is in Scotland for their annual break in the highlands. But this is a particularly poignant moment as two of her immediate three heirs – William, 33, and 2-year-old George – are alongside her as the 89-year-old monarch becomes the longest-reigning monarch in British history.

Insiders are playing down talk of a special dinner to mark the occasion. And other members of the royal family continued with engagements around the country. Camilla, the Duchess of Cornwall, spent the day at a television studio marking the 60th anniversary of Britain’s ITV, while Prince Charles had an engagement at Dumfries House, the historic estate he helped save in Scotland.

For William and the family, it is a time to reflect on the Queen’s contribution to the country. Last month, he praised his grandmother for being a “model for a life of service” in a book written ahead of another impending landmark – her 90th birthday on April 21.