Displaced people from the minority Yazidi sect, who fled from the violence in the Iraqi town of Gwer, wait to return at a check point.. Reuters GWAIR, Iraq—Sunni families in northern Iraq are being prevented from returning to their homes, suspected by their neighbors and Kurdish authorities who control the area of collaborating with the extremist group Islamic State. The offensive by the Sunni militants is threatening to reshape the demographics of once-mixed communities by dividing territory along ethnic and religious lines, Iraqi and Kurdish officials say. Kurds, Christians and other minorities were driven from their homes by the insurgents’ rapid advance. But even after Kurdish forces, aided by U.S. airstrikes, wrested back control of some of the towns, many are refusing to move back if their Sunni Arab neighbors are also allowed to return. Kurdish security forces have been screening Sunni Arabs for ties to Islamic State fighters […]