John of Gaunt had a mistress, Katherine deRoet, from whom the Beauforts descended. (Katherine’s sister, Phillipa, was married, unhappily, to Geoffry Chaucer) Katherine was John’s mistress through two marriages and they married after the second wife’s death. The Church of England eventually gave full privileges to Katherine and John’s bastard children, the Beauforts, from whom the line has descended. (”Katherine” by Anya Seaton, is an entertaining novel covering the whole period)
I read that book in my ‘teens. John of Gaunt is one of the key figures of the period, a classic strongman.
Regarding the article, piffle. The connection between the Mountbatten-Windsors and the House of York is completely irrelevant. Parliament made William of Orange king, and Parliament made George of Hanover king.