Mary (1505–1558), Queen of Hungary 

Mary of Hungary was the fourth daughter and youngest child of Philip the Fair and Joanna the Mad, and the sister of the Holy Roman Emperors Charles V and Ferdinand I. She was married, at the age of nine, to Louis II Jagellon, who became king of Bohemia and Hungary the following year, in 1516. Her husband was killed in 1526 in an equestrian accident fleeing a losing battle ...