Conquerors saga (Kiersten White)

No one expects a princess to be brutal. And Lada Dragwlya likes it that way. Ever since she and her gentle younger brother, Radu, were wrenched from their homeland of Wallachia and abandoned by their father to be raised in the Ottoman courts, Lada has known that being ruthless is the key to survival. She and Radu are doomed to act as pawns in a vicious game, an unseen sword hovering over their every move. For the lineage that makes them special also...

To build the country she wants, Lada, the brutal ruler of Wallachia, must destroy everything that came before, including her relationships with brother Radu and former love Mehmed, Sultan of the Ottoman Empire.