Prince Albert II of Monaco and his wife Princess Charlene, Prince Jacques, Princess Gabriella and Kaia-Rose Wittstock stand on the palace balcony during the celebrations marking Monaco's National Day in Monaco. Pictures: Reuters

It seems like a minute ago since SA-born Princess Charlene gave birth to her twins - Princess Gabriella Thérèse Marie and Prince Jacques Honoré Rainier. 

The twins who are now a month shy of their fifth birthdays made a very rare public appearance with their parents to celebrate Monaco’s National Day.

The two joined other members of the royal family on the palace balcony. And, according to the principality’s ruler, the number of marriages and births which have swelled the Grimaldi family ranks in just the past few years created something of a royal traffic jam on the balcony.

"We’re running out of space for everyone," Prince Albert II told PEOPLE. "We’re going to have to create new windows, build new balconies." 

Princess Charlene of Monaco, Prince Jacques and Princess Gabriella stand on the palace balcony during the celebrations marking Monaco's National Day in Monaco.

On a serious note, he added, "It is actually an issue. Before we used to have family and high-ranking staff from the palace, people who worked with us very closely from the household stand in the windows."

He later joked: "I don’t think I can face up to another christening or wedding right now," before adding, "Actually, it’s great feeling to have that many new members of the family and everybody seems to get along well."

Prince Albert II of Monaco and his wife Princess Charlene stand on the palace balcony during the celebrations marking Monaco's National Day in Monaco.

Dressed for the occasion, Princess Gabriella Thérèse Marie wore a pretty red beret, along with a red frilly dress. Prince Jacques Honoré was dressed in full military regalia.

Prince Albert II of Monaco, his wife Princess Charlene and Prince Jacques stand on the palace balcony during the celebrations marking Monaco's National Day in Monaco.

The two obviously take their royal duties very serious and could been seen waving at the crowds below.

Prince Albert II of Monaco and his wife Princess Charlene, Prince Jacques, Princess Gabriella and Kaia-Rose Wittstock stand on the palace balcony during the celebrations marking Monaco's National Day in Monaco.

Princess Charlene looked demure in an all-white ensemble, styled with a hat tilted to the side.