Princess Josephine of Denmark, 13, wore her mother Queen Mary's old Prada coat for King Frederick's proclamation

Princess Josephine made a special nod to her mother on the day she became Queen of Denmark.

The 13-year-old looked like her mother's doppelgänger as she appeared on the balcony of Christiansborg Castle in Copenhagen following the proclamation of HM King Frederik X and HM Queen Mary of Denmark.

Thousands of people gathered outside Christiansborg Castle on Sunday, prepared with folding chairs and waving Danish flags in the hope of catching a glimpse of the royals.

And Josephine, who along with her twin brother Prince Vincent is the royal couple's youngest child, echoed her mother's style for the historic occasion.

In a sweet gesture, Josephine donned a navy double-breasted coat from Prada, the same piece Mary wore in 2013.

To complete her look, the young royal added a pair of her mother's custom Dulong Fine Jewelery rose quartz earrings – a piece Mary has worn continuously over the years – including at the Danish UN Mission reception in New York last October.

Josephine combined her mother's pieces with accents of her own style and added a piece of black ribbon in her hair.

The 13-year-old, who celebrated her birthday a week before her parents took the throne, completed the look with a pearl necklace.

It comes after a body language expert said Princess Josephine is the Danish royal family's 'version of Prince Louis'.

Adrianne Carter said the sassy young teenager stole the show and was 'at the forefront' as the family stepped out again to join the adoring crowd at Amalienborg Palace – after their first performance in Christiansborg.

“Her older brother gives her a gentle touch to remind her to keep her behavior in check,” she added, commenting on Josephine's twin brother, Prince Vincent.

The duo waved excitedly to the crowd, while their older brother Prince Christian, 18, and sister Isabella, 16, offered more subdued waves.

The newly crowned King and Queen of Denmark – Frederik and Mary – also shared a soft kiss.

Queen Mary of Denmark previously wore the navy double-breasted Prada coat during an outing in 2013

Queen Mary of Denmark has worn the Dulong Fine Jewelery rose quartz earrings several times, including in New York last October (photo)

Josephine looked sophisticated as she waved to the crowd alongside her twin brother Prince Vincent

The children had also previously been on the balcony of Christiansborg Castle with their parents to celebrate this memorable day.

King Frederik

It also marked a big moment for the now Crown Prince Christian, who became the first in line for the Danish throne on Sunday afternoon.

The 18-year-old waved proudly to the hundreds of royal spectators gathered under the balcony, smartly dressed in a navy blue suit and white shirt.

His younger brother Vincent was just as smart in a matching navy blue suit, but opted for a pink and blue striped tie instead of the block color his older brother wore.

Princess Isabella, 16, went for a striking red ensemble, with her hair pulled back into a sleek bun. She waved enthusiastically to the crowd and sang along to their rendition of the Danish national anthem.

Mary and Frederik were joined by their four children: Christian, Isabella, Vincent and Josephine

Maria was a vision in white as she joined her husband on the balcony shortly after he was proclaimed King of Denmark by Prime Minister Mette Frederiksen

Her younger sister Josephine, 13, was a little shyer and hid behind her mother.

But Mary quickly reassured her with an arm around her waist, and she too waved to the crowd below in her navy blue peacoat.

There is little doubt that Frederick's accession to the throne will mark a turning point for the Danish royal family, which has so far grown up relatively normally.

They live away from the public eye, attend public schools and remain close to the Australian side of the family, including their grandfather, Scottish-born math professor John Donaldson.

The children – and royal parents – are seen as often in puffa coats and combat trousers as in suits, heels and dresses.

They enjoy taking their Australian border collies Grace, Coco and Chloe for walks, attending football matches and skiing.

Appearances and grace are not encouraged at home. The family was captured dressed casually – Mary in glasses and a woolen sweater, Isabella in a denim shirt – to decorate their Christmas tree in December.