When Henry died in the January of 1547, Katherine was once again a widow. Her step-son, Edward, was now King, and his Uncle, Edward Seymour, Lord Protector. Thomas Seymour, her former lover, renewed his suit, and Katherine married him within months of the King’s death. The two were very much in love, but the impulsive and ambitious Admiral was not the best choice of husband she could have made. He was jealous of his brother’s position of Lord Protector, and when thirteen year old Elizabeth came to live with him and Katherine, he took a perverted interest in his young charge and began to make inappropriate visits to her bedchamber. At first Katherine thought his interest was innocent, but then she grew jealous and sent Elizabeth from her household. By now Katherine was expecting her first child and was not very well.
On the 30th of August 1548, Katherine went into labour and was delivered of a baby girl. The child was named Mary and Lady Jane Grey was her godmother. Less than a week later, however, Katherine was dead. Like Jane Seymour, she fell ill of puerperal fever, and died on the 5th of September 1548. No one knows what became of her daughter, Mary. The child was still alive in 1550, a year after Thomas Seymour, her father, was executed for treason, but afterwards disappears from history. An eighteenth century legend says she married a man called Sir Edward Bushel, and went on to have children, but in all likelihood she died in infancy.
Katherine was given a funeral befitting her status and was buried in St Mary’s Church, next to Sudeley Castle.