<ion-router-outlet> is not working in ionic 4

Ionic Framework
1

Hi i am trying to add two child pages in parent page with two tabs in ionic 4 using below code but i was confused about ion-router-outlet not showing admin with two tabs,when i select tabs respective pages have to show but its directly showing child1 page

I wan wondering when i use router-outlet its working fine please suggest me some one where did i do wrong?

admin.html

<ion-content padding>
  <ion-row>
    <ion-col col-4><button ion-button color="secondary" (click)="child1()">Child1</button></ion-col>
    <ion-col col-4><button ion-button color="secondary" (click)="child2()">Child2</button></ion-col>
  </ion-row>
  <ion-router-outlet></ion-router-outlet>

</ion-content>

admin-router.module.ts

const routes: Routes = [
    {
        path: 'Admin',
        component: AdminPage,
        children: [
            { path: '',redirectTo: '/Admin/Child1',pathMatch: 'full'},
            { path: 'Child1', component: Child1Page },
            { path: 'Child2', component: Child2Page },
        ]
    }
];

adminModule.ts

@NgModule({
    imports: [
        CommonModule,
        IonicModule,
        AdminRoutingModule
    ],
    declarations: [
        AdminPage,
        Child1Page,
        Child2Page
    ]
})
export class AdminModule {

}