From the time of her marriage, Catherine became known as Mistress Knollys, and from as Lady Knollys. She married Edward Stalker. Issue[ edit ] Sir Francis and Lady Knollys produced a number of offspring who survived to maturity. Some contemporaries also asserted that Catherine was an illegitimate child of Henry VIII , which would make her Elizabeth's half-sister. Although this was never acknowledged by the King, Catherine was given deference by the Court as she aged and came to resemble Henry.