Who is Tyr Varanday from The False Princess and what is their importance?

Tyr Varanday is the son of a merchant in Treb. Tyr seems to like Sinda and she appreciates their friendship. Over the course of the novel, Sinda's feelings deepen. Sadly, shortly after she realizes that her feelings for Tyr are romantic, she overhears him telling his friends about his determination to sleep with Sinda, the woman who was raised as a princess.