Joanna was born on 6 November 1479 in Toledo, the capital of the Spanish kingdom of Castile. She was a clever and excellent student, and she was married to Duke Philip the Handsome of Burgundy at the age of sixteen in 1496. She married Philip by proxy in Valladolid, and she gave birth to six children from 1498 to 1507. In 1502, she became Princess of Asturias, making her heir to the Castilian throne; in 1504, she became Queen of Castile and Leon after her mother's death, with Philip serving as the jure uxoris king. Her father, Ferdinand II of Aragon, declared himself her guardian, claiming that her mental illness prevented her from ruling, and he was proclaimed her regent. Philip died in 1506, having been poisoned by Ferdinand, and Ferdinand served as king until his death in 1516. Ferdinand had initially intended to make his favorite grandson, the future Ferdinand I of Germany (with whom he shared his name, culture, and even birthday), his heir; however, he was pressured to make his other grandson and Joanna's son Charles the new King of Spain with Joanna as queen consort. From 1517, she was nominally co-monarch with Charles, and she died in 1555; her son abdicated just one year later, and he died in 1558.