Originally Posted by Te Mirdala Mand'alor
He's talking about the attribute bonus that the PC gets when you've mastered either side of the force (completely dark/light). I don't think the party members can get that.
I've been able to do it with some modded Xbox saves (Getting my companions to Light/Dark Mastery). I had to set the Exile's CHAR to 20. This also works in the PC version or you can set their Good/Evil to 100 for Light Mastery and 0 for Dark Mastery using KSE.