Not all Orange is Daily Kos

The darling daughters:
Amalia, Alexia and Ariane on holiday in Argentina [source]

Guilherme Alexandre, príncipe de Orange
This photograph was produced by Agência Brasil,
a public Brazilian news agency. [Source: Wikipedia]

The Dutch Coat of Arms

Today we feature His Royal Highness Willem-Alexander , Prince of Orange, Prince of the Netherlands, Prince of Orange-Nassau, Jonkheer van Amsberg. His full name is Willem-Alexander Claus George Ferdinand van Oranje-Nassau, but he used the surname "van Buren" when running in the New York City Marathon.

Wikipedia (the main source of information for this post) tells us he is an aircraft pilot and sportsman. He is also the eldest son and heir of Queen Beatrix of the Netherlands. He has two younger brothers: Prince Friso and Prince Constantijn.
Willem-Alexander was born on April 27, 1967. Although he had not planned to marry until in his 40s, a certain young lady changed his mind. "[O]n February 2, 2002, he married Máxima Zorreguieta Cerruti ..., an Argentine woman of Spanish, Basque, and Italian ancestry who, prior to their marriage, worked as an investment banker in New York City."
The Prince and Máxima have three daughters: Catharina-Amalia Beatrix Carmen Victoria (Amalia for short), Alexia Juliana Marcela Laurentien, and Ariane Wilhelmina Máxima Ines.
Assuming that Willem-Alexander will succeed to his mother's throne, he will be the first male Dutch monarch since 1890 and will be known, in English, as King William IV of the Netherlands.
His page on the Dutch royal website is here.

The Prince was not always interesting in royal duties and may well have been a handful. A profile in Hello Magazine says this:

But his increasing rebelliousness and problems with his parents meant that the teenage prince was sent to Atlantic College near Cardiff for a two-year course, where he gained an International Baccalaureate in 1985. "I had problems with my parents at the time," said Willem-Alexander in a TV interview much later. "And my parents had problems with me. So it was best for us to split up."

After the obligatory military service – it is compulsory in the Netherlands – which was spent in the Royal Netherlands Navy, Willem-Alexander studied history at Leiden University, gaining his degree in 1993. But books did not interest him nearly as much as flying planes did and, after gaining his Military Pilot's Licence, Willem-Alexander immersed himself back in the armed forces, spending several months studying at the Netherlands Defence College. He has since flown humanitarian relief missions in Kenya and even acted as pilot for his country's politicians, ferrying government ministers to meetings abroad.

Beyond family he has an unusual interest:

But his real interest lies in water management – above all in Eastern Europe – and he is both honorary member of the World Commission on Water for the 21st Century and patron of the Global Water Partnership, a body established by the World Bank, the UN and the Swedish Ministry of Development Cooperation.

All right, time to move to videos: