Who is Thom of Trebond. from In the Hand of the Goddess and what is their importance?

Thom of Trebond is a powerful sorcerer. He is also Alanna's twin brother. Thom and Alanna traded places, so that he could go on to study magic, and she could become a warrior. Thom loves his sister, but he has become harder and more isolated since the death of their father. He also finds himself disliked by his peers for his great skill, as well as his superior attitude. He has passed his Master tests at a young age and is isolated because of his skill and personality.