Although James VI of Scotland succeeded Elizabeth I upon her death in 1603, he was not the rightful successor according to Henry VIII’s last will and testament, which stipulated that the heirs of Henry’s younger sister Mary, duchess of Suffolk would inherit the throne in the event of his three children (Mary I, Edward VI and Elizabeth I) dying childless. By that reasoning, Lady Katherine Grey’s eldest son Edward Seymour, Lord Beauchamp was the rightful king of England, not James VI of Scotland. However, the ruling of an ecclesiastical commission in 1562 that Katherine’s marriage was invalid and her sons illegitimate would have prevented recognition of Edward as Elizabeth’s successor.
Born in 1540, Katherine is thought to have been named after Queen Katherine Howard, who became the fifth wife of Henry VIII that year. Like the queen, Katherine Grey incurred royal disfavour and suffered disgrace as a result.
Like her sister Lady Jane Grey, Katherine was imprisoned in the Tower of London, but – unlike Jane – she is thought to have been held in the Bell Tower.
Katherine is popularly regarded as the most beautiful of the three Grey sisters, although there is no surviving contemporary description of her appearance.
During the early years of Elizabeth’s reign, a conspiracy developed that sought to marry Katherine to Don Carlos, son and heir of Philip II of Spain. The Habsburgs favoured Katherine’s claim because of their hostility to the English succession rights of Mary, Queen of Scots who was married at that time to the Dauphin François – France was Spain’s traditional enemy.