Smoothing groups shared across Objects

[NateG81]

So I am currently working on a character customization system and can't seem to figure out a way to have multiple objects in the same smoothing group.

I am working on a face, each area seperated into it's own object (mouth, eyes, ears, nose). Is there any way to identify all those meshes as being part of the same smoothing group?

Currently there is a change in smoothing groups where the eye mesh meets the mouth mesh that creates a difference in lighting.