One of the things I discuss in my book on Edward VI is whether or not there was likelihood that Arthur, Fitzroy, and Edward all received a mutated CRFT gene (inherited an atypical cystic fibrosis) from both parents. After a quick romp in the genealogy I am slightly surprised that royal babies weren’t born three eyes; the inbreeding is extreme. The sons and grandsons of Henry VII were all decedents on both sides of their parents from the same group of Plantagenet.
Take Arthur for example. His father was Henry VII’s, and the king’s maternal great-grandfather was John of Gaunt, who was one of the sons of Edward III and therefore a direct descendant of the Plantagenet king, Henry II. Henry VII’s grandmother was Catherine of Valois, who was also descended from Henry II by his grand-daughter Blanche of Castile via a marriage to King Louis VIII of France. Thus, Arthur’s father was descended from Henry II on both sides. Arthur’s maternal line was also descended Henry II. His mother, Elizabeth of York, was the direct descendant of Edward III from his son Edmund of Langley. Clearly, if there was a recessive gene for a CFTR mutation in the Plantagenet DNA, Arthur had multiple chances of inheriting it from his multiple Plantagenet ancestors. Arthur was practically his own cousin.
Arthur’s younger brother also bred back into the Plantagenets to get his sons Henry Fitzroy and Edward IV. Fitzroy was Henry VIII’s illegitimate son with Bessie Blount, and Blount was descended maternally from Henry II through his grandson Richard, the 1st earl of Cornwall. Edward’s mother, Jane Seymour, was also descended maternally from Henry II through Edward III’s son Lionel of Antwerp. Although the mutuality of their ancestors was not as extreme as Arthur’s, there was still multiple ways a recessive gene could have been passed on to Fitzroy and Edward through the Plantagenet bloodlines.
My, what a tangled genealogical web royalty wove!