Take out dynamic required and invisible

Contacts are never companies
Add labels

partner_firstname/partner_view.xml

@@ -33,9 +33,11 @@
         </field>
         <!-- Add firstname and last name in inner contact form of child_ids -->
         <xpath expr="//form[@string='Contact']/sheet//field[@name='category_id']" position="before">
-           <group attrs="{'invisible': [('is_company', '=', True)]}">
-            <field name="lastname" attrs="{'required': [('is_company', '=', False)]}"/>
-            <field name="firstname"/>
+          <group>
+            <label for="lastname" class="oe_edit_only"/>
+            <field name="lastname" required="1" nolabel="1"/>
+            <label for="firstname" class="oe_edit_only"/>
+            <field name="firstname" nolabel="1"/>
           </group>
         </xpath>
         <xpath expr="//form[@string='Contact']/sheet//field[@name='category_id']" position="attributes">