Falling in love with your best friend's little sister is never a good idea. Getting caught kissing her, that's even worse.I watched Lizzie Donovan grow up - from pigtails and scraped knees to pouty lips and lush curves.It wasn't until one night nine years ago in the front seat of her car, with her lips on mine, that I realized what I was feeling was far more than friendship.Of course, I felt her brother's wicked left hook shortly after.One promise was all it took to push her away.Not anymore.This is my chance.I have three months to convince her that she's the song in my heart and we're more than just forbidden lyrics.