The King's Bastard

The King's Bastard (King Rolen's Kin, Book One) - Rowena Cory Daniells

This book turned out better than I first thought it would be.The author did a great job on world-building,and I really liked the characters.
In some cases didn't like.
The story is centered around one noble family,parents who were basically forced into marriage and their four children.Three boys and a
girl.One boy is supposed to take the throne,his twin a formidable fighter.The younger brother banished to a monastery because he has
affinity, which in this book is a type of magic.And the daughter who is kind of bull-headed when it comes to rules.And they want to marry
her off for the good of the kingdom.

Everything takes place in a unheard of land with unheard of beasts.It's always cold and they travel on frozen rivers.