I am not really all keen to marry into a Royal Family but if I married, I would have to bee really madly in love.
Anyway the only Royal Family I might marry into (because I love it so much, so in my case it's marrying into family literally) is the British Royal Family. My age group limits me to Prince William and Prince Harry, so I would probably marry one of them. But, believe me or not, I never thought of marrying either of them (though I like both), I am perfectly happy as I am, a commoner!:) :p
Queen Elizabeth: "I cannot lead you into battle, I do not give you laws or administer justice but I can do something else, I can give you my heart and my devotion to these old islands and to all the peoples of our brotherhood of nations." God, Save The Queen!