The Luck of the Irish.(Niall Horan fanfic)

What if your whole life was based on a lie?What if the ones you loved turned on you?What if you had a sister you didnt even know about,but not just a sister,a twin sister?Well this is what happens to Rebecca,she's just 15...Way to young for NIall....Right?What if stupid management forced Niall to break up with you?Nia...