Catherine of Aragon was legally married to
Henry VIII's older brother,
Arthur, in accordance with the laws of the land. The case later cited for petition of
annulment by Henry VIII was that the first marriage was never
consumated, as Arthur was too ill to consumate the marriage.
Catherine of Aragon was the youngest surviving child of Ferdinand and Isabella of Spain. As was common for princesses of the day, upon her birth, her parents began looking for a political match for her. At three years of age, she was betrothed to Arthur, the son of Henry VII of England. Arthur was not quite two at the time.
When she was almost 16, in 1501, Catherine made the journey to England. It took three months, and her ships weathered several storms, but she made landfall at Plymouth on October 2, 1501. Catherine and Arthur were married on 14 November 1501 in Old St. Paul's Cathedral, London. Catherine was escorted by the groom's younger brother, Henry.
Following the wedding and celebrations, the young couple moved to Ludlow Castle on the Welsh border. Less than six months later, Arthur was dead, possibly of the 'sweating sickness'.
By 1505, when Henry was old enough to marry, Henry VII wasn't as keen on a Spanish alliance, and young Henry was forced to repudiate the betrothal. Catherine's future was uncertain for the next four years, during which time she was given an inadequate allowance and was forced to sell many of her own possessions in order to sustain her household. When Henry VII died in 1509, one of the new young king's actions was to marry Catherine. She was finally crowned Queen of England in a joint coronation ceremony with her husband Henry VIII on June 24, 1509.
Shortly after their marriage, Catherine became pregnant. This first child was a stillborn daughter born prematurely in January 1510. This was soon followed by another pregnancy. Prince Henry was born on January 1, 1511 and was christened on the 5th. There were great celebrations for the birth of the young prince, but they were halted by the baby's death after 52 days of life. Catherine then had a miscarriage, followed by the birth of a son who died shortly after being born. On February 1516, she gave birth a daughter named Mary, and this child lived. There were probably two more pregnancies, the last recorded in 1518.
Henry was growing frustrated by his lack of a male heir, but he remained a relatively devoted husband. He had at least two mistresses: Bessie Blount and Mary Boleyn.
By 1526 though, he had begun to separate from Catherine because he had fallen in love with one of her ladies (and sister of one of his mistresses): Anne Boleyn. (Though it should be added that supposedly he never lost respect for Catherine's intellect.)
She lived for the next three years imprisoned in several dank and unhealthy castles and manors with just a few servants, and was not permitted to see her daughter. She seldom complained of her treatment, though she steadfastly refused to acknowledge the annulment of her marriage.
On January 7, 1536, Catherine died at Kimbolton Castle and was buried at Peterborough Abbey with the ceremony due for her position as Princess Dowager. (There's a step down from your coronation as queen).
Catherine of Aragon wore the habit of a nun under her court robes. She was not a happy woman, (after 25 years of marriage Harry says, "We're not married.")?? But rest assured, she was no harridan.
Note: The write-up to which I was responding originally said that Henry and Catherine were not legally married and that she was a harridan.