The brothers fit what European anti-terrorism investigators call a disturbing but now-familiar profile. They were young Belgian nationals of Moroccan descent, both with extensive criminal records involving violent crime and guns. But neither had been previously linked to terrorism, Belgium's chief prosecutor, Frederic Van Leeuw, said Wednesday at a news conference here. The siblings — Brahim and Khalid El Bakraoui — were publicly identified Wednesday as two of the suicide bombers in attacks at an airport and on a metro train Tuesday that left 31 people dead and 260 injured, the latest terrorist strikes to stun a continent reeling from...