The origins of Berradin Pack are unknown beyond the fact that they are most likely ancient Celts from around the area currently known as Scotland. They are ancient, although the oldest known pack member is Mason Berrin, father to Corran and Hamish.
There are thought to be some satellite (bachelor) werewolves who were Berradin, but this is only speculation.
Werewolves have a very specific heirarchy, and the Berradin pack follows this heirarchy. The individuals inhabiting the pack heirarchy alters with subsequent books, so giving a rundown of their status within the pack would potentially spoil books future and past. It could also become quite confusing trying to keep up with the changes. Therefor, please read here to find out more about pack heirarchy, and enjoy learning about the changes from within the books themselves.