Mengambil submenu di router.js pada vue

Layouts Sidebar.vue

<ul>
        <li v-for="(item,index) in items" :key="item.path">
          <router-link :to="item.path">
            <i :class="item.icon"></i>
            <span>{{item.name}}</span>
          </router-link>
        </li>
      </ul>

  created(){
  this.$router.options.routes.forEach(router => {
      this.items.push({
        name:router.name,
        path:router.path,
        icon:router.icon,
      })
    })
  },

Router

import Vue from 'vue'
import Router from 'vue-router'
import Layout from '@/layouts'
Vue.use(Router)

export default new Router({
  mode: 'history',
  base: process.env.BASE_URL,
  routes: [
    {
      path: '/',
      name: 'Home',
      icon: 'fa fa-home',
      redirect: '/dashboard',
      component: Layout,
      children: [{
        path: '/dashboard',
        name: 'home',
        component: () => import('@/views/Home.vue'),
      }]
    },
    {
      path:'/todo',
      name: 'Todo',
      icon: 'fa fa-user',
      redirect: '/todos',
      component: Layout,
      children: [{
        path: '/todos',
        name: '',
        component: () => import('@/views/Todo.vue'),
      }]
    },
    {
      path:'/profile',
      name: 'Profile',
      redirect: '/nested/menu1',
      children:[
        {
          path: 'menu1',
          component: () => import('@/views/About'), // Parent router-view
          name: 'Menu1',
          meta: { title: 'Menu1' },
          children: [
            {
              path: 'menu1-1',
              component: () => import('@/views/Profile'),
              name: 'Menu1-1',
              meta: { title: 'Menu1-1' }
            },
          ]
        }
      ]
    }

  ]
})

bagaimana cara mendapatkan children didalam children . jika children hanya ada satu dan tidak nested maka itu parent. jika children memiliki nested itu children yang akan diambil dan di masukan ke ul