Bail Organa. There is more legend attached to this name then there is actual fact. Along with Mon Mothma, Ben Kanobi, and others, he was one of the Old Order. He had fought the Clone Wars along side the likes of Ben Kanobi, and was one of the leaders of the early Rebel activities. When Leia was to be seperated from her mother to protect her from Darth Vader and the Emperor, he adopted her and raised her as his own daughter.
He was the ruler of Alderaan; a peaceful planet. And because he was the ruler, Leia got the title of Princess! When the first Death Star exhibited it's power for the very first time, it was unfortunate that the choice had to be Alderaan. Bail Organa and millions of other innocent lives were lost. In effect, this is when the Rebel uprising begins.