How to do this?

I have a Parent Table. "Some" Parents have Children. Using a one-to-many mapping I get an empty Set for parents with no children and a Set of children for the parents with children. So far so good...

Now, if I create a criteria for the children Set, I only get parents that have children.

I want to be able to get all parents. And for those parents that have children, I want the children that meet some condition.

This seems like a simple thing, yet I can't figure it out...

Thanks!!!