We Few: Prince Roger Series, Book 4

Prince Roger is coming home, but home isn't what it was when he left. Traitors have murdered his brother and sister, his nieces and nephews. His mother, the empress, is still alive but in the hands of Roger's own biological father, who controls her through drugs and physical and psychological torture. A new heir to the throne has been conceived, and once the child is born his mother will no longer be necessary to the traitors' plans. Prince Roger must somehow retake the empire from the men who control it before his new brother is born and his mother dies. It's an impossible task, but Prince Roger knows all about impossible tasks.