How do you pass data between VueJS components when using a Vue router?

I have this routes setup:

Vue.use(Router)
export default new Router({
  routes: [
    {
      path: '/group/:id',
      name: 'Group',
      component: GroupContainer,
      children: [
        {
          // when /group/:id/posts is matched
          path: 'posts',
          component: ViewPosts
        },
        {
          // when /group/:id/topics is matched
          path: 'topics',
          component: ViewTopics
        },
        {
          // when /group/:id/people is matched
          path: 'people',
          component: ViewPeople
        }
      ]
    }
  ]
})

      

        
        
        
      

    

So the group component has a template with a router view here

<template>
  <div class="group">
    I am a group page
    <router-view></router-view>
  </div>
</template>

      

        
        
        
      

    

Thus, the group bean becomes the parent of ViewPosts, ViewTopics, or ViewPeople, but it does not directly contain the components.

What is a good system for passing data from parent (Group) to children (ViewPosts ...) and allow children to emit parent?