You can override bundles by defining the function getParent in your bundle class. I think the name getParent is a little confusing. It's like your bundle is the child and another bundle the parent.

The child overrides the parent, this is normal. But in Symfony we call the Parent and we get the code of the overriden Child. That sounds anormal...

I suggest to call this function overrides or extends or something like that. But there is no Parent-Child relation between Bundles.