Royal Twins

it was announced last week that the Crown Princess of Denmark is pregnant with twins. She is due to give birth in January.
Twins run in families. Twins are genetic. I was a twin, and twins run through my ancestral lines.
Queen Margrethe II's first cousin, Count Christian af Rosenborg, is the father of twins daughters, Camilla and Josephine. The former Prince Flemming of Denmark, who was created Count af Rosenborg, when he married Ruth Nielsen, was the father of twin sons, Axel and Birger.

The Luxembourg royal family has two sets of twins: Prince Jean and Princess Margaretha, the children of Grand Duke Jean and Grand Duchess Josephine Charlotte. Grand Duke Jean and Grand Duchess Josephine Charlotte's youngest son, Prince Guillaume, is the father of a set of twins: Leopold and Charlotte. Prince Laurent and Princess Claire of the Belgiums have twin sons, Aymeric and Nicolas.

The late Princess Margarete of Prussia and her husband, Friedrich Karl, Landgraf of Hesse, were the parents of two sets of twin sons: Philipp and Wolfgang, who were born in 1896, and Richard and Christoph, who were born in 1901. Philipp's grandson, Hereditary Prince Heinrich Donatus, and his wife, Floria, are the parents of Paulina and Moritz, born in 2007.

Earlier this year, the Countess of Mornington, the wife of Earl of Mornington, whose grandfather is the Duke of Wellington, gave birth to Mae and Arthur. Mae was born first, but Arthur is the eventual heir to the Wellington Dukedom. Lord Mornington's mother, Princess Antonia of Prussia, is a twin. She has a brother, Prince Rupert. In May, Doña Margarita, the wife of Don Luis Alfonso de Borbon y Martinez-Bordiu, gave birth to twin sons, Luis and Alfonso.

Princess Maria Pia of Italy and her first husband, Prince Alexander of Yugoslavia, are the parents of two sets of twins, Dimitri and Michel and Serge and Helene. It is understood that the second set of twins were actually fathered by Prince Michel de Bourbon-Parma, Maria Pia's second husband. Maria Pia was still married to Alexander when the twins were born, which makes them members of the Yugoslav royal family. (A moot point as the male line descendants of the late Prince Paul have never had dynastic rights in Serbia/Yugoslavia.)
Crown Prince Alexander of Yugoslavia and his first wife, Maria da Gloria, are the parents of twin sons: Philip and Alexander.
Other royal twins include:

Prince Caspar and Prince Christian of Waldeck und Pyrmont
Prince Jaime and Princess Margarita of Bourbon-Parma
Prince Gundakar and Princess Dietmut of Liechtenstein
Archduchesses Monika and Michaela, daughters of Archduke Otto
Prince Umberto and Princess Sofia of Bulgaria
Prince Jacques and Prince Michel of France
Duke Huno and Duke Johann of Oldenburg
The Hon. Timothy and the Hon. Nicholas Knatchbull
Princess Marie-Gabrielle and Princess Marie-Charlotte of Bavaria
Friedrich, Prince of Hohenzollern, and Prince Franz Joseph of Hohenzollern
Benedikta and Adelgunde of Hohenzollern, twin daughters of Prince Friedrich
Berengar and Marina Patterson, twin children of Princess Viktoria Marina of Prussia, and her American husband, Kirby Patterson.
Christian and Phiilipp Prinz von Preussen, the sons of Prince Adalbert of Prussia, who is the nephew of Princess Viktoria Marina.
Prince Franz Wilhelm and Prince Franz Joseph of Prussia (the latter lived for only 23 days)
Prince Albrecht and Prince Ruprecht of Hohenlohe-Langenburg
Prince Josias and Prince Johannes of Waldeck und Pyrmont