Daughter of Philip III of Spain and Margarethe of Austria.  The future King Charles I of England, accompanied by his best friend, the Duke of Buckingham, travelled to Spain, incognito, to woo her in person.  The Spaniards made up a song:
 
    Carlos Estuardo soy/ Que siendo amor mi guia/ A cielo d'Espana voy/ Per ver estrella Maria  (Charles Stuart am I/ By love brought from afar/ To the skies of Spain I come/ To see Maria, my star.)
 
    However, since Charles refused to become a Catholic, and Maria refused to marry a heretic, his courtship came to nothing.  Maria married her cousin Ferdinand (III) of Austria, as it had always been intended that she should.  The reports of the Archduke's physical and mental development that had reached Madrid had not been encouraging, but Maria knew her duty far too well to complain.  having steeled herself to endure marriage to a deformed idiot, she was so delighted to find him physically and mentally normal, that she fell in love with him!  Fortunately, the feeling was mutual, so they lived happily ever after.

Source: Sandra White