He was born under the reign of a usurper, Henry IV, who had stolen the throne from his cousin Richard II, and would one day attempt to usurp the throne from Henry IV’s grandson, Henry VI. Although Richard would die, his son Edward would finish the job of stealing the crown … only to have his brother Richard steal it in turn from Edward’s sons (the 3rd Duke’s grandsons). Then, with what could be further karmic irony, Richard III was overthrown and murdered by the grandson of Henry VI’s maternal half-brother, who was crowned Henry VII. However, Henry VII married the 3rd Duke of York’s granddaughter, and thus the comingled bloodlines the usurper Henry IV and the usurper Edward IV would rule together as the tyrannical Henry VIII.
The rules of inheritance for monarchs in England was as much “what comes around goes around” as it was based on lineage.
That’s not to say that the 3rd Duke of York didn’t have a fine lineage. He was descended from King Edward III on both sides of his family. His mother, Anne Mortimer, was the great-granddaughter of Edward III’s second surviving son, Lionel of Antwerp. On his father’s side the duke was the grandson of Edmund of Langley, 1st Duke of York the fourth surviving son of King Edward III. It could be argued (and it was!) that as a direct descendant of Edward III’s second son the duke was more rightfully heir to the throne than Henry VI, whose grandfather Henry V was the eldest son of King Edward III’s third surviving son, John of Gaunt.
Of course the real heir to Edward III’s throne by his eldest son, Richard II, had died (suicide or murder; no one knows for sure) when Henry IV grabbed the throne … so the entirety of the Ward of the Roses was a squabbling among usurping wannabe’s.
The fight for the crown was as bloody, merciless, and self-interested as the fight to be Alpha Male in a troop of chimpanzees.