2 Samuel 13: The rape of Tamar, the murder of Amnon, and the flight of Absalom

Because of David's multiple wives, the prophesy of Nathan (that the sword will never leave David's house) manifests itself. Amnon's lust for his half-sister, Tamar, leads to rape.
David is unable to properly discipline, so Absalom takes it upon himself (two years later) to avenge his sister, taking Amnon's life.
Absalom seems to have learned much from his father's earlier misdeeds -- but is forced to flee back to the home of his maternal grandfather.
David is angered by the events, but also misses Absalom out of sentimentality.