Adds new and clearer definitions for servicemembers, veterans, and family relationships and creates a 26-workweek leave entitlement to care for covered servicemembers and certain veterans who cannot work because of serious injury or illness. It updates rules about intermittent leave, notice and certification requirements, continuation of health benefits, and enforcement under both the Family and Medical Leave Act (private-sector and covered employers) and the statutory leave rules that apply to Federal employees (Title 5).