Black Wolves Saga -Bloody Nightmare-

The protagonist, Fiona lived in a secluded tower due to her fragile health. There is turmoil in the country and a severe disease outbreak known as Zodiva or “Mad Wolf Disease”. Mejojo was interested in Fiona due to her upbringing and wanted to take her as his bride, but Fiona’s father refused. There are now rumours in town saying Fiona is a witch- Mejojo and Auger uses this to their advantage and arrest her, so that they can “observe” her while she lives in the castle. Eventually, Fiona’s half-brother (Nesso) and butler (Zara) rescue her and they escape together.
The emphasis of the story is on a dark/historical/political fantasy where humans, wolves, cats and other animals are being ruled by two very crafty feline tyrants. Due to various oppressions the cat twins faced in their childhood including assassination attempts, they learned how to survive and gain power- but they were also driven towards insanity. There is nothing they won’t do to get what they want.

[From White Prayer's review]