Fluent many-to-many: Deleting one end does not remove the entry in the relation table

Question

I have two classes (Parent, Child) that have a many-to-many relationship that only one end (Parent) knows about. My problem is that when I delete a "relation unaware" object (Child), the record in the many-to-many table is left.

I want the relationship to be removed regardless of which end of it is deleted. How can I do that with Fluent NHibernate mappings, without adding a Parents property on Child?

The classes:

public class Parent
{
    public Guid Id { get; set; }
    public IList<Child> Children { get; set; }
}

public class Child
{
    public Guid Id { get; set; }
    // Don't want the property below:
    // public IList<Parent> Parents { get; set; }
}

The many-to-many mapping for the Children property on Parent looks like this:

mapping.HasManyToMany(parent => parent.Children)
    .LazyLoad();