Katherine (or Catherine - spelling in the Middle Ages was far from standardized) Parr was Henry VIII's sixth and last wife; she was chosen mainly because she had already survived two husbands and the aging and increasingly sickly Henry needed someone reliable to care for him - not to mention she wouldn't be as troublesome as his last wife, the teenaged Kathryn Howard, who fooled around quite publicly and was summarily beheaded.
In addition to being an exceedingly patient nurse and loving stepmother to Mary, Elizabeth, and Edward, Katherine was the most intellectual of Henry's wives. She had been well educated and was devoted to scholarly pursuits and Protestantism, and made sure that Henry's younger children had the best tutors available, such as Roger Ascham and John Cheke. Her chambers were often the center of lively theological debate, and this very nearly got her in trouble; when Henry was in a bad mood one day and sick of hearing his wife's radical religious lectures, he threatened to have her arrested for heresy. He did offer her a chance to get back into his good graces, though, by allowing her to agree with him in a religious argument for once, which she did cheerfully. The King declared them "friends again" and personally beat the men who came to arrest her the next day.
Other than that, their marriage was, for the most part, an untroubled one. Katherine and Henry may not have been madly in love, but the evidence seems to point to them liking each other a great deal. They argued, but always made up speedily; Henry lavished Katherine with gifts and she was often found perched on his lap when his infected leg wasn't troubling him too much. However, Henry grew sicker and sicker over the course of their three-and-a-half-year marriage, and finally Katherine was a widow for the third time in January 1547, at the age of about thirty-five.
She had been prudent and patient her whole life, but shortly after Henry's death, she decided she could wait no longer and married Thomas Seymour, whom she had loved since before her marriage to the King, in the spring of 1547. Many people thought it indecent, but Katherine, by that point, apparently did not care. She and Seymour lived happily for just over a year, counting the future queens Elizabeth and Lady Jane Grey as members of their household, but their marital bliss was cut short when Katherine died of puerperal fever shortly after giving birth to a daughter, Mary, in August 1548. She was buried in St. Mary's Church at Sudeley Castle, and her grave can still be seen there today.