...
    <class name="MyOwningEntity">
        <id name="id">
            <generator class="org.hibernate.id.SequenceGenerator">
                <param name="sequence">hibernate_sequence</param>
            </generator>
        </id>
        <map name="keyValueMap" cascade="all">
            <key column="MY_OWNING_ENTITY_ID" />
            <map-key-many-to-many column="KEY_ID" class="MyKeyEntity" />
            <many-to-many column="VALUE_ID" class="MyValueEntity" />
        </map>
    </class>
...
</hibernate-mapping>