Me? My name is Jenna. Jenna Bieber. Yes yes it's true I'm Justin's sister. That's all I hear when I have to give out my full name. Then it's usually followed by a beg for an autograph or picture of him. I'm 15! I don't carry around a picture of my older brother in my purse! That's creepy! Even if he is teen pop idol sensation Justin Bieber.