class Parent {
    private Set childs;
}

<hibernate-mapping>
<class name="Parent" table="PARENT">
   <id name="uuid" type="string" unsaved-value="null">
      <column name="parentUid" length="64" not-null="true" />
         <generator class="assigned" />
   </id>      

        <set name="childs" inverse="true" cascade="all">
      <key column="parentUid" />
      <one-to-many
         not-found="ignore"
         class="Child" />
      </set>
   </class>
</hibernate-mapping>

class Child {
   private Parent parent;
}

<hibernate-mapping>
<class name="Child" table="CHILD">
   <id name="uuid" type="string">
      <column name="assignmentUid" length="64" not-null="true" />
      <generator class="assigned" />
   </id>
      
   <many-to-one name="parent" class="Parent" column="parentUid" not-null="true" />
</class>
</hibernate-mapping>

Child = new Child();
parent.add(child);
session.save(parent);