Well, from the beginning (X-Men), it was obviously Mystique, Sabretooth, and Toad.
In X2 he didn't have a Brotherhood.
But in X-Men: The Last Stand, it would have been:
-Mystique*
-Pyro
-Callisto
-Arclight
-Quill
-Juggernaut
-Multiple Man
* = Mystique was a main member until she got cured.