Margaret would be the last princess born to a reigning English monarch until the birth of  who's wife?
Margaret, Countess of Pembroke Margaret of England (20 July 1346 – October/December 1361) was a royal princess born in Windsor, the daughter of King Edward III of England and his consort, Philippa of Hainault. Margaret would be the last princess born to a reigning English monarch for over a century, until the birth of Elizabeth of York in 1466. She was also known as Margaret of Windsor.
Mary FitzRoy, Duchess of Richmond and Somerset Mary FitzRoy, Duchess of Richmond and Somerset (Howard; 1519 – 7 December 1557), born Lady Mary Howard, was the only daughter-in-law of King Henry VIII of England, being the wife of his only acknowledged illegitimate son, Henry FitzRoy, 1st Duke of Richmond and Somerset.