Daughters of the formidable Isabella and Ferdinand of Spain, Katherine and Juana were born into a world of privilege and luxury that came at a devastating personal price. They were trained from an early age to understand European diplomacy and were useful as a way to secure new alliances through marriage. Katherine's marriage to Prince Arthur appeared to go well until he died suddenly but her subsequent marriage to King Henry VIII did not result in the vital heir. Juana fared no better with Philip of Burgundy, whose ambition and cruelty made her life equally difficult.