author Agnes Strickland claimed, in her biography of Katherine Parr, that Mary Seymour did survive to adulthood, and in fact married Sir Edward Bushel, a member of the household of Anne of Denmark, wife of King James I. Strickland's theory suggested that the Dowager Duchess of Suffolk, after her marriage to Richard Bertie in 1553, and before she fled England during the Marian Persecutions in or after 1555, she arranged Mary's marriage to Bushel. The problem with this theory is that Mary would have been aged six at the time. Another theory states that Mary was removed to Wexford, Ireland, and raised under the care of a Protestant family there, the Harts, who had been engaged in piracy off the Irish coast under the protection of a profit sharing arrangement with Thomas Seymour. A lozenge-shaped ring inscribed "What I have I hold" was reputed to have been an early gift to Thomas by his brother Edward, and was passed down through generations of the Seymour-Harts until at least 1927. There was reference to "Mary" found in old Elizabethan texts of 'The Late Queen's heir.' However, this could be various other women. Historian S. Joy states that "Mary definitely lived past the age of 10, but after that little is known." A more modern theory, from Linda Porter, author of a 2010 biography on Katherine Parr, suggests that a 1573 Latin book of poems and epitaphs written by John Parkhurst, Katherine Parr’s chaplain, contains the following reference to Mary: I whom at the cost Of her own life My queenly mother Bore with the pangs of labour Sleep under this marble An unfit traveller. If Death had given me to live longer That virtue, that modesty, That obedience of my excellent Mother That Heavenly courageous nature Would have lived again in me. Now, whoever You are, fare thee well Because I cannot speak any more, this stone Is a memorial to my brief life Porter suggested that this was an epitaph written by Parkhurst on the occasion of Mary's death, around the age of two. Porter further speculates that Mary is buried in Lincolnshire, near Grimsthorpe, the estate owned by the Duchess of Suffolk, "where she had lived as an unwelcome burden for most of her short, sad life."
Portrayals in fiction
The story The Red Queen's Daughter by Jacqueline Kolosov centres around Mary Seymour, and speculates a life in which she never marries, and becomes lady-in-waiting to Queen Elizabeth I. The novel The Stolen One by Suzanne Crowley states that Mary survived and was raised by a 'witch' in the English countryside. A similar premise allows Seymour's supernatural powers to help her friend Alison Bannister search for her lost child in The Phantom Tree by Nicola Cornick.
