Delphine Boël grew up certain that she should be a princess. Now a court ruling and a DNA test could make it true.

Ms. Boël, 50, is a Belgian visual artist who claims that she was conceived during an extramarital affair between King Albert II of Belgium and Ms. Boël’s mother, Baroness Sybille de Selys Longchamps.

The court ruling, published Monday, gave credence to her claim and ordered Albert to submit DNA evidence to determine whether he is Ms. Boël’s biological father.