She was born into royalty — and then erased from history. Mary Seymour was the only child of Queen Katherine Parr, the sixth and final wife of Henry VIII. Her birth in 1548 should have secured her a place in the Tudor legacy. Instead, it marked the beginning of one of England’s quietest historical mysteries. Mary’s life unraveled almost as soon as it began. Her mother died just days after giving birth, likely from complications related to childbirth. Her father, Thomas Seymour — ambitious, reckless, and politically dangerous — was executed for treason less than a year later. By the time Mary was two years old, she was an orphan.…