Cool! I'm related to Black Jack Pershing.
I read all the historical novels about the queens by Victoria Holt and the Anya Seton ones, when I was a girl, but I haven't picked up many of the more recent biographies.
However, a recent book about Anne Boleyn gave the impression that there's little more fact to the "nonfiction" books than the fiction, because the sources are so limited.
Weir’s book makes that same point about the dearth of information. It all occurred during the great plague outbreaks in Europe in the 14th and 15th centuries.
The Gaunt in John of Gaunt actually referred to Gent, Belgium. The deRoet’s came from that area. Today, here, the name is Roets.