I have this horrible fantasy..im so ashamed?

im a girl and im a teen. I have this disguisting Fantasy about . I dont know why but it really turns me on..BUT its not my own family members who i think about..i think about some random people who are family members having . Not people i know but like stars or somthing and just pretend their related. I'd never ever do this kind of thing with my own family...ewww.I Love my family alot but not in that way...yuck. AND NO IM NOT FROM THE SOUTH. But i feel really gross about it sometimes. Im really ashamed... whats wrong with me? is this bad??.