Princess Peach Toadstool is a character in the critically acclaimed Super Mario series. In the series, she usually portrays the princess in distress, and has been kidnapped by Bowser in almost every game. In the original game, she possessed a special power that would allow her to reverse the black magic of the Koopa clan, thus giving Bowser a reasonable answer to why he would kidnap the princess, as he was at the time using it to cast a spell on all of the Mushroom Kingdom's residents. Another reason could be, that the Koopa king got, like many others, a crush on the mushroom-princess, like he expressed in his diary.
Mario and Luigi, the protagonists of the series, always seem to rescue the princess and save the Mushroom Kingdom when needed. Other characters also lend a helping hand, such as Yoshi, Wario and a cast of other characters in the Mario RPGs.
She is the sole ruler of the powerful Mushroom Kingdom. While it doesn't seem like she has a father, her trusty longtime steward Toadsworth seems to act as some kind of father figure toward her, and is always keen on keeping her safe (though because of his age, he is not able to stop the forces of Bowser's army). (Her father has been mentioned in the first Nintendo Adventure Book Double Trouble)