There were 2 Joan Beauforts. 1st Joan Beaufort was the daugbter of John of Guant (PLANTAGENANT) and his mistress and later wife, Katherin Swynfords..The 2nd Joan Beaufort was the daughter of John Beaufort (the son John of Gaunt and Katherine Swynford, and brother of the 1st Joan Beaufort).. The 2nd Joan Beaufort was the daughter of Margaret Holland (and John Beaufort), and was also the Queen Consort of Scotland and wife of King John of Scotland from 1424 to 1437..