Queen Mary puts on united front with King Frederik on Amalienborg Palace balcony as she matches in pink with mother-in-law Queen Margrethe for her husband's birthday

King Frederik and Queen Mary put on a united front as they appeared on the Amalienborg Palace balcony for the monarch's birthday today.

The father-of-four is celebrating his first birthday since he ascended the throne today and greeted crowds of royal fans who had gathered outside the residence.

For the occasion, Mary opted for a bright pink long-sleeved dress, which perfectly matched her mother-in-law's fuchsia frock.

Mary's dress featured a ruffled drop hem and voluminous gathered sleeves. The royal styled her brown hair in loose waves and wore an elegant gold bangle.

Queen Mary and King Frederik have been plagued with rumours of marital struggles since the King was pictured enjoying an evening out in Madrid with Mexican socialite Genoveva Casanova last year.

Pictured: King Frederik and Queen Mary of Denmark seen waving to crowds from the Amalienborg Palace balcony 

The publication of the photos resulted in Genoveva, 47, issuing a statement denying any kind of romantic relationship between herself and the royal and slamming the 'malicious' rumours. 

Frederik and Mary were joined on the balcony by their four children Crown Prince Christian, 18, Princess Isabella, 17, and twins Prince Vincent and Princess Josephine, 13. 

Isabella cut a sophisticated figure in a blue floral printed wrap dress with balloon sleeves.

Meanwhile, her younger sister Josephine looked elegant in a light blue-and-white floral knee-length dress with sheer sleeves. 

The family-of-six were joined on the balcony by Queen Margrethe, 84, who abdicated in January following a 52-year reign.

The mother-of-two looked glamorous in a bright pink midi dress with short sleeves.  

Sweeping her hair up into her signature bun, Margrethe showcased a dazzling flower-shaped brooch. 

Earlier today, the Danish Royal Household has released a new portrait of King Frederik to mark the monarch's 56th birthday. 

Frederik opted to wear his military uniform for the new portrait, which was posted on Instagram this morning.

Pictured: Frederik and Mary were joined on the balcony by their four children Crown Prince Christian (centre), 18, Princess Isabella (far right), 17, and twins Prince Vincent and Princess Josephine (left), 13 and Queen Margrethe, 84

The father-of-four is celebrating his first birthday since he ascended the throne today and greeted crowds of royal fans who had gathered outside the residence. Pictured with daughters Josephine (left) and Isabella (right)

Pictured: King Frederik seen waving to crowds of royal fans in Copenhagen who wished him a happy 56th birthday

King Frederik looked dapper in a navy suit and red tie as he waves to crowds from the Amalienborg Palace balcony today

The royal's black double-breasted jacket was adorned with his Air Force badge and his military citation bars.

In 1995, the Crown Prince began his service as a member of Denmark's elite special operations forces, the Royal Frogmen Corps. He also completed training in both the army and air force in his younger years.

Posing against a dark grey background, Frederik also opted for a plain black tie and crisp white shirt. 

Later today, the royal is set to appear with Queen Mary and their children on the Amalienborg Palace balcony.

In the caption, the Royal Household informed royal fans of how Frederik and the family will mark his birthday today.

It read: 'His Majesty the King has a birthday and is turning 56 today. 

Pictured: The official birthday portrait of King Frederik, which was released by the Danish Royal Household this morning

'The birthday is marked at 12.00 in Amalienborg, where the King and the Royal Family appear on the balcony of Frederik VIII's Palace.

'The audience is invited to take part in the festive celebration of the King at the Castle Square.'

What's more, fans can also send their well wishes to the King via the Danish Royal Family's website.

The post continued: 'In addition, everyone has the opportunity to wish His Majesty a happy birthday on the Royal House's social media as well as the website, where a digital congratulatory list has been created for the occasion.' 

The King  ascended the Danish throne with his wife Queen Mary in January after his mother Queen Margrethe abdicated following a 52-year reign.

In the caption (pictured), the Royal Household informed royal fans of how Frederik and the family will mark his birthday today

Pictured: King Frederik and Queen Mary of Denmark following the monarch's proclamation in January

The former monarch signed her historic abdication papers with her son and grandson Prince Christian, 18, present in Christiansborg Palace in Copenhagen.   

The Queen's last words before leaving the Council of State were: 'God save the King.'

Following this, the new King addressed the crowds that had gathered outside the royal palace from the balcony.

Earlier this month, King Frederik and Queen Mary celebrated their 20th wedding anniversary during a state visit to Norway.

Mary and Frederik donned matching padded navy and canary yellow gilets, with the Queen donning a black and white striped long-sleeve t-shirt and her husband wearing a plain white shirt. 

Australian-born Mary and Frederik's 23-year romance was often dubbed a 'real-life fairytale' after they met in a Sydney pub. 

But pictures emerged of the monarch having an evening out with Mexican socialite Genoveva Casanova - the former daughter-in-law of the billionaire Duchess of Alba - in November last year.

The pair were seen walking through Madrid before heading to her apartment building, changing clothes and heading out again for the evening.