The protagonist is the daughter of the king who dies during one of the battles in the book. She is aided by her best friend, Owen (I think that was his name), who is the son of a witch and a healer. He can also use magic. There are elements of fantasy in this series like vampires that aren't a main part of the book. At the last battle at the end of the book, the vampires appear at the battlefield with the young queen or queen to be, don't remember which. I think Owen proposed to her or confessed at that battle. The romance is really subtle. The book is mainly action. In the second book of the series, they're married with children, and the youngest daughter is the only child with magic. She is full of jealousy and hatred toward her family except for her father. She aided the invading army in their second attempt to take over the country. The main protagonist is the queen's son who was born with a limp. He had to leave with the refugees, and learned how to fight on a mount at the country he arrived at. When Owen found out about his youngest daughter's treachery, he cast her into the darkness, to his dark side of the family. I think the title was Land of the... something but it's been 4-5 years since I've last read the book.

The Cry of the Icemark, Blade of Fire, and The Last Battle of the Icemark by Stuart Hill. This trilogy is one of my all time favorites. Glad I could help.