Also known as Catherine Knollys or Lady Knollys.
(Born around 1524- Died January 15, 1569)
Daughter of Mary Boleyn and William Carey.
Married to Sir Francis Knollys.
Mother of Mary Stalker, Sir Henry Knollys, Lettice Knollys, Countess of Essex, William Knollys, 1st Earl of Banbury, Edward Knollys, MP, Sir Robert Knollys, MP, Richard Knollys, MP, Elizabeth Leighton, Lady Leighton, Sir Thomas Knollys, Sir Francis Knollys, MP, Anne West, Lady De La Warr, Catherine, Baroness Offaly, Lady Butler, Maud Knollys and Dudley Knollys.

Catherine Carey was the daughter of Mary Boleyn, the sister of Anne Boleyn, and William Carey. She was the mother of Lettice Knollys and the Chief Lady of the Bedchamber to Queen Elizabeth I.

Catherine Carey was born around 1524 to Mary Boleyn and William Carey. William Carey was from Aldenham in Hertfordshire. He was a Gentleman of the Privy Chamber and Esquire of the Body to Henry VIII. Her parents were married in 1520 and soon after, it is believed that Mary Boleyn started her affair with Henry VIII. Contemporaries have claimed that Catherine Carey was in fact an illegitimate child of Henry VIII, but there is no evidence to support this claim and Henry VIII never acknowledged her as his own child. It is said that Catherine was a witness to Anne Boleyn’s execution, but that is simply not true.

Catherine would become a Maid of Honour for both Anne of Cleves and Katherine Howard. It is believed that Catherine met her future husband Francis Knollys when he was part of the group that welcomed Anne of Cleves to England in November 1539. We do not know if their families arranged the marriage or if the king had a hand in the match, but Catherine and Francis were married on April 26, 1540. The couple had fourteen children, including Lettice Knollys. Francis Knollys was knighted in 1547 and Catherine was called Lady Knollys. During the reign of Mary I, Francis and Catherine took part of their large family and fled to Germany because they were very staunt Protestants.

In January 1559, Catherine and Francis returned to England after the death of Mary I and the succession of Elizabeth I. Sir Francis Knollys was appointed Vice-Chamberlain of the Royal Household and Catherine was made Chief Lady of the Bedchamber. Elizabeth never supported the claim that Catherine was her half sister, but for the ten years that Catherine served Elizabeth, she was seen as one of Elizabeth’s favorites at court and her favorite first cousin. Catherine Carey would die on January 15, 1569 at Hampton Court Palace and she was buried in St. Edmund’s Chapel in Westminster Abbey.

Sources:
https://en.wikipedia.org/wiki/Catherine_Carey
https://www.theanneboleynfiles.com/26-april-1540-the-marriage-of-catherine-carey-and-francis-knollys/