Karen Healey writes at Strange Horizons about the problematic nature of parents and families in YA, whether you include them or not:
Most young people in the real world don't live independent of their family (many adults also live with family members, of course, but it's easier to justify creating those who don't, should one be inclined to do so). Parents, in particular, pose a problem for writing young adult fiction. In reality, they tend to be more or less active presences, shaping activities and schedules, providing boundaries which can't be broken without consequence, and otherwise providing the sweet, sweet conflict that feeds the writing of compelling plot. In a lot of realistic YA fiction, conflict with family and parents is a major theme, and there's a lot of great work that deals with the complexities of family relationships.
She also includes the thoughts of several other writers–Brenna Yovanoff (The Replacement), Jackie Dolamore (Magic Under Glass), Tara Kelly (Harmonic Feedback) and Cynthia Jay Omololu (Dirty Little Secrets). Well worth checking out.