AddressFieldset.vue

<template>
  <fieldset>
    <div class="field">
      <label>Rua</label>
      <input type="text" :value="data.street" @change="event => $emit('input', { street: street })" />
    </div>
    ...
  </fieldset>
</template>

<script>
  export default {
    props: {
      data: {
        type: Object,
        default: () => ({})
      }
    }
  }
</script>

ClientForm.vue

<template>
  <form @submit="send">
    <address-fieldset :data="data" @input="update" />
    ...
    <button type="submit">Enviar</button>
  </form>
</template>

<script>
  import AddressFieldset from './AddressFieldset'
  ...

  export default {
    components: {
      AddressFieldset,
      ...
    },
    data () {
      return {
        street: 'Av. Paulista',
        ...
      }
    },
    methods: {
      change (fields) {
        this.data = { ...this.data, ...fields }
      },
      send () {
        ...
      }
    }
  }
</script>