My understanding is that the other 10(?) clans in the federation came out of the Catti tribe that Malcolm the 1st allowed to settle in Scotland around 1100AD a Celtic tribe from the low lands of Europe. From what I've seen lately, it doesn't actually function, as I was a member for a while, but haven't received any information in several years.
IF I remember what I read a while back the chief of McIntosh or McPherson are considered the head of the federation. Who exactly is the head depends on which clan you recognize. At least they are feuding...