title: Validate before creating objects and create multiple models data through one serializer
body: <p>I created multiple models related to an applicant</p>
  <pre><code>class Applicant(models.Model):
      app_no = models.CharField(max_length=20, unique=True)
  
  class ApplicantBasicDetails(models.Model):
      applicant = models.ForeignKey(Applicant, on_delete=models.CASCADE)
      f_name = models.CharField(max_length=255, blank=True, null=True)
      m_name = models.CharField(max_length=255, blank=True, null=True)
      l_name = models.CharField(max_length=255, blank=True, null=True)
      gender = models.CharField(max_length=15, blank=True, null=True)
  
  class AppplcantFamilyDetails(models.Model):
      applicant = models.ForeignKey(Applicant, on_delete=models.CASCADE)
      relation = models.CharField(max_length=255, blank=True, null=True)
      f_name = models.CharField(max_length=255, blank=True, null=True)
      m_name = models.CharField(max_length=255, blank=True, null=True)
      l_name = models.CharField(max_length=255, blank=True, null=True)
      gender = models.CharField(max_length=15, blank=True, null=True)
  </code></pre>
  <p>Now developing an API where someone will POST below body</p>
  <pre><code>{
      &quot;app_no&quot;: &quot;123456&quot;,
      &quot;applicant_basic_details&quot;: {
          &quot;f_name&quot;: &quot;&quot;,
          &quot;m_name&quot;: &quot;&quot;,
          &quot;l_name&quot;: &quot;&quot;,
          &quot;gender&quot;: &quot;&quot;
      },
      &quot;applicant_family_datails&quot;: [
          {    
              &quot;relation&quot;: &quot;&quot;,
              &quot;f_name&quot;: &quot;&quot;,
              &quot;m_name&quot;: &quot;&quot;,
              &quot;l_name&quot;: &quot;&quot;,
              &quot;gender&quot;: &quot;&quot;
          },
          {
              &quot;relation&quot;: &quot;&quot;,
              &quot;f_name&quot;: &quot;&quot;,
              &quot;m_name&quot;: &quot;&quot;,
              &quot;l_name&quot;: &quot;&quot;,
              &quot;gender&quot;: &quot;&quot;
          }
      ]
  }
  </code></pre>
  <p>I don't have much idea how to validate multiple models data first before creating objects I wrote one serializer.</p>
  <pre><code>class AllInOneSer(serializers.Serializer):
  
      def create(self, validated_data):
          app_no = validated_data.pop(&quot;app_no&quot;)
          app_ser = ApplicantSer(data={&quot;app_no&quot;: app_no})
          if app_ser.is_valid():
              pass
          else:
              return &quot;error&quot;, app_ser.errors
  </code></pre>
  <p>How can I pass these multiple models data through one serializer, to validate and create objects?</p>