Sure. 

I imagine it was the er, the king of Hiertania from two generations before, aka the grandfather of the Princes, who surprisingly is still alive and kicking. Eternal Life potions and magic may have been involved. 

Unlike his son, his reign was characterized by turmoil and war. He did his best to keep his citizens and retainers safe, but he was not very charismatic and gained a ghastly reputation, probably not helped by the fact that he dabbled in occult stuff and any kind of thing that would give him an edge against the threats of the kingdom. His title of Witch King was entirely deserved.

So he made a difficult decision when his sons were of age. He abdicated the throne, as someone who had so much blood in his hands and reign was not fit for ruling during peace time and sentenced himself to a life of exile, trying to find the answers to philosophical questions, and helping those in need, as an atonement for his past war sins. Of course as events as they are he might come out of hiding. He could feel guilty that the Second Crown Prince most likely used some of the alchemic treatises he left in the palace.

Edit: Can also make a Witch Queen if it flows better :D