Daughters of ruin

Princesses Rhea, Cadis, Suki, and Iren were raised as sisters, but they are not. In fact, their fathers, kings of rival kingdoms, were enemies, but when King Declan brought the four girls together, the kingdoms agreed on a truce on the condition that the four girls would eventually take their respective thrones in peace. Nothing is that simple, of course, and the "sisters" hate each other--until Declan's palace is attacked and the four are thrown together for survival.