Karl V was a tall, muscular ruler with dark eyes and a commanding presence. He ruled over a vast empire stretching from Spain to the Americas. His first wife, Isabella of Portugal, tragically died in 1539 during the birth of their daughter, Catherine, after complications in childbirth. She was just 35. Karl’s children—Philip II (15), Maria (13), Joanna (10), and Catherine (8)—became his main focus.