Retired Gen. David Petraeus began an affair with his biographer in 2011, two months after he became CIA director, a friend and former top aide said Monday. The case has sparked an uproar in Congress over FBI investigative tactics and complaints by lawmakers they weren’t told soon enough about the probe rocking the intelligence and law enforcement establishment. Petraeus, who resigned last week as the nation’s head spy, and his family are said to be devastated over the affair, especially his wife Holly, who “is not exactly pleased right now,” said Steve Boylan, a friend and former Petraeus spokesman who …