Question: Whose birth is celebrated by the annual holiday where Oranjegekte occurs?

Context paragraphs:
Freda Betti: Freda Betti (26 February 1924 – 13 November 1979), whose birth name was Frédérique Thérèse Augusta Betti, was a French mezzo-soprano singer whose career was mainly confined to France.  She left a range of recordings representative of her repertoire.

Valentine's Day: Valentine's Day, also called Saint Valentine's Day or the Feast of Saint Valentine, is an annual holiday celebrated on February 14.  It originated as a Western Christian liturgical feast day honoring one or more early saints named "Valentinus", and is recognized as a significant cultural and commercial celebration in many regions around the world, although it is not a public holiday in any country.

Costa Rican passport: Costa Rican passports are issued to Costa Rican citizens to travel outside Costa Rica.  Currently, it is valid for 6 years (10 years before 2006).  It is issued to people born on Costa Rican soil (who are citizens by default), and to children of Costa Rican citizens born abroad, who are reported to the nearest Costa Rican embassy (whose birth, immediately after such report, is recorded in the civil registry).  Children born overseas to a Costa Rican citizen are Costa Rican by birth, not by naturalisation, as stated in the Constitution of Costa Rica.

Iglehart House: The Iglehart House is an Italianate style house in the Morgan Park neighborhood of Chicago, Illinois, United States, and one of the city's oldest surviving buildings.  Located at 11118 S. Artesian Avenue, the original portion of the house in the back was built in 1857 by an unknown architect for Charles D. Iglehart, whose farmstead comprised the land now bounded by 111th, 115th, and Rockwell streets and Western Avenue.  Iglehart's daughter Mary, who was born in the house in 1857, is the first child whose birth is recorded in what would become the village of Morgan Park.  Iglehart was one of the founders of The Church of the Mediator, whose first building was built in 1889 at 110th and Hoyne Avenue on land that was donated for it by the Blue Island Land and Building Company.  Due to the space required of a growing family, the two-story front portion of the house was added in the 1870s.  It was designated a Chicago Landmark on July 13, 1994.

Furuta Oribe: Furuta Oribe (古田 織部 , 1544 – July 6, 1615) , whose birth name was Furuta Shigenari (古田 重然 ) , was a daimyō and celebrated master of the Japanese tea ceremony.

Koningsdag: Koningsdag (] ) or King's Day is a national holiday in the Kingdom of the Netherlands.  Celebrated on 27 April (26 April if the 27th is a Sunday), the date marks the birth of King Willem-Alexander.

Mother's Day (United States): Mother's Day in the United States is an annual holiday celebrated on the second Sunday in May.  Mother's Day recognizes mothers, motherhood and maternal bonds in general, as well as the positive contributions that they make to society.  It was established by Anna Jarvis, with the first official Mother's Day was celebrated at St. Andrew's Methodist Church in Grafton, West Virginia, on May 10, 1908.

Oranjegekte: Oranjegekte (Orange craze) or Oranjekoorts (Orange fever) is a phenomenon in the Netherlands that occurs during major sporting events, especially international football championships, and during Koningsdag, an annual holiday celebrating the king's birthday.  It manifests itself in the wearing of orange clothing such as T-shirts, caps and scarfs; lavish attention for sports and sports fans in the media; and the decoration of cars, rooms, houses, shops, and even entire streets in orange, the traditional color of the Dutch royal family, the House of Orange-Nassau.

Flooding of the Nile: The flooding of the Nile (Arabic: عيد وفاء النيل‎ ‎ ) has been an important natural cycle in Egypt since ancient times.  It is celebrated by Egyptians as an annual holiday for two weeks starting August 15, known as "Wafaa El-Nil".  It is also celebrated in the Coptic Church by ceremonially throwing a martyr's relic into the river, hence the name, Esba` al-shahīd ("The Martyr's Finger").  Ancient Egyptians believed that the Nile flooded every year because of Isis's tears of sorrow for her dead husband, Osiris.

Tryphine: Saint Tryphine (also spelled Trifine, Triphine and Tréphine) is a semi-legendary Breton saint whose life is often considered to be the basis of the story of Bluebeard.  In Brittany she is widely revered as a patron saint of sick children and those whose birth is overdue.  The legend of Saint Tryphine probably derives from a historical individual who was the wife of the early Breton ruler Conomor.

Supporting paragraphs: Oranjegekte Koningsdag
Answer: King Willem-Alexander