I thought that the Kingdom of Netherlands was older than that.

I don't know my History, really.

It's good to have a joyful event to celebrate.
Oh my goodness ! Those sleeves...

This outfit doesn't suit her well. Well, every taste are in Nature, as we say in France.

I suppose it's a Nathan creation because every time I see a princess/queen in something I dislike, it's Nathan's work.

Before becoming a kingdom the Netherlands have predominantly been a republic or annexated by a foreign power (Habsburg, Spain etc).
Instead of kings etc the united Low Countries had stadtholders (Dutch: stadhouder) In the Low Countries, the stadtholder was a medieval function, which during the 16th, 17th and 18th century, developed into a rare type of de facto hereditary head of state of the thus "crowned" Dutch Republic. It is comparable with the French title Lieutenant and England's 16th century Lord Lieutenant. The Dutch Monarchy is a cognatic descendant of the first Stadtholder of the young Republic, William of Orange.
Officially the first king of the Netherlands was the Frenchman Louis Napoléon (brother of the French Emperor Napoléon). He was succeeded by prince Willem Frederik of Orange-Nassau, who was the son of the last stadtholder Willem V.
Stadtholder Willem III is also known as King William III of England (and Ireland).