- Mary, Queen of Scots was the heir by primogeniture, but Catholic, foreign-born and pro-France.
- Margaret Douglas was the senior native-born heir by primogeniture, but Catholic and excluded from the succession by Henry VIII.
- Catherine Grey was the heir in accordance with the succession laws set down by Henry VIII and Protestant (although she seems to have informed the Spanish she would convert if they helped her). A prisoner in the Tower and involved in an unpleasant ?marriage? with Edward Seymour, by whom she had two ?illegitimate? sons.
- Mary Grey, sister of Catherine, is the heir if Catherine and her ?bastards? are set aside. She was deformed and unmarried, making it likely Catherine's son would succeed her.
- Margaret Clifford, Countess of Derby, is the heir according to Henry VIII's will if you consider the Grey sisters to have forfeited their rights by their "involvement" in their sister's usurpation of the throne. Protestant, married with two sons.
Closest male candidates would be Henry Stuart, Lord Darnley, or Henry Hastings, Earl of Huntingdon, the great-grandson of Margaret Plantagenet (next-in-line in the Yorkist succession after Elizabeth of York's descendants) and Henry Stafford, 2nd Duke of Buckingham (senior descendant of Edward III's youngest son Thomas of Woodstock), who was her cousin many times over.