Can I set a custom pivot point for an empty GameObject?

I must rotate a group of objects relative to a certain pivot point (including the main camera itself). They are all under a parent empty GameObject. So it would be cool if I can specify the point in x, y coordinates for the parent object. How can I achieve that? Should I add a component or what?

Yeah, I just created another empty object for parent and position it accordingly.

Missing the simplest things sometimes…