I personally don't think that FOB is below me taste wise (I'm 21) because a lot of what I feel the songs talk about go over a teenager's head. I know that at 17 when I first discovered them I really didn't get some of the bigger things talked about.
Also when it comes to music, unless it's OBVIOUS marketed to a younger audience (like Miley, Selena, Demi, and the Jonas Brothers) I don't think it's wrong or weird to enjoy them. Also, a lot of pop artists were originally discovered/loved by teenage girls so it's not always a bad sign when the fan base starts out that young. You just gotta keep an eye and see if the fans grow with it or drop off all around the same time.