Katherine de la Pole

Katherine de la Pole was the oldest daughter of Michael de la Pole, 2nd Earl of Suffolk and Katherine de Stafford.

She became abbess of Barking Abbey. In this capacity, she took care of Edmund and Jasper Tudor, the two eldest sons of Catherine of Valois (widowed queen of King Henry V of England) by her second husband Owen Tudor. She persuaded King Henry VI to take an interest in the boys, who were his half-brothers. Henry later ennobled them, thereby taking one of the important steps that would later enable Edmund's son Henry Tudor to claim the English throne.

...
Wikipedia