Cormac was a 14th century Irishman. He was the husband of Sorcha, the father of Tadhg and the brother of Niall.
Cormac and Sorcha had Victoria Waterfield stay with them while the Second Doctor and Jamie McCrimmon took care of some business. During this time, first his son, then his wife, and finally he himself succumbed to the Black Death. (PROSE: Screamager)