Unity - Avatar problem?

Alright, so I have a small but annoying problem. I have two models of hand_left and hand_right and they are both joined together via a GameObject which is the prefab. So my problem is I have a controller but the I can't set anything as a avatar since the avatars are both on the left hand and the right hand. How do I get a merged avatar for both?

Sorry for the kinda long post but hopefully I could get some quick answers here.

I will appreciate any suggestions, thanks alot!