mistress of John Beaufort

From "Margaret Beaufort's illegitimate sister"

"John Beaufort was held captive in France from 1421, when he was captured at the Battle of Bauge, until he was ransomed in 1438 and it was during this time that he fathered two illegitimate children by unknown French women. The son was called John and the daughter was called Tacine or Thomasine. .... Tacine was born in about 1434 in France, this date is the one most commonly attributed to her, however it seems that she would then be only about twelve or thirteen when she married which seems very young. Due to the age of her husband, a date of 1425 seems more likely for a birth date.