Mathew Trewhella III was the spouse of Jennie Trewhella and later Mellina making him the father of Conor, Sapphire, and Mordowrgi. He was also a descendant of Mathew Trewhella I and the second Mathew Trewhella, and they share the same name and similar fates. Mathew Trewhella III was formerly human, but after entering Ingo he eventually became one of the Mer. He was technically killed by Mortarow, but could be considered as killed by Ervys.