After the sudden death of Henry V in 1422, Catherine was effectively exiled from court, suspicion falling on her nationality. The regents kept her away from her child, and she turned for comfort to Owen Tudor, a Welsh courtier, who would become the founding father of the Tudor dynasty. Although Catherine was forbidden by a new law to marry again, there was a general lack of interest in her on the part of the authorities which enabled her to form a liaison with, and possibly to marry secretly (but, if so, it was legally invalid), Owen Tudor, and give birth to at least four children.
Their daughter died young, and their son Owen became a monk, but their other two sons, Edmund Tudor and Jasper Tudor, were to play an important role in the future of the English monarchy. Catherine died in childbirth on January 3, 1437, in London, and was buried in Westminster Abbey. Her husband or lover, Owen Tudor, lived on until 1461, when he was executed by the Yorkists following the Battle of Mortimer's Cross. Their sons were given earldoms by King Henry VI after Catherine's death. Edmund would become the father of the future King Henry VII of England.