Error in routing in angular ver. 2+ ?

Question

I was creating a routing, without children it was working fine, but when i added children then it generates an error, please look into code :

{path:'', redirectTo:'/students', pathMatch:'full'},
{
       path:'students',
       component:StudentsComponent,
       children:[
           {path:'',component:StudentStartComponent},
           {path:':id',component:StudentDetailComponent},
           {path:':id/edit',component:StudentEditComponent}
           {path:'new',component:StudentEditComponent},
        ]
 },
{path:'subjects-list', component:SubjectsListComponent},

 But in the above code, i have an issue "cannot read property studentId".