Tolcan is a prince in title only. While his twin brother is throwing extravagant parties, Tolcan is drinking with the lower class and sleeping with a variety of women. But one nomad has caught his interest. A royal with a nomad is rarely done, but a prince falling for a man is unheard of in Sarid.
Ki is a threat to the royal bloodline which is the magical source that powers the barrier that surrounds the kingdom. If the king discovers that Tolcan is involved with a man, he could order Ki to be imprisoned or even killed.
Tolcan hides the relationship from his father even though he may not even be the next king. It is law for there to be only one prince, but with twin boys, the king must choose who will be his heir. Thankfully, it's been clear for years that his father favors his brother, Albern, while Tolcan is seen as the extra prince. Rather than fight for the king's attention, Tolcan embraces his position. But Albern's magic is limited while Tolcan excels.
The king is the main source of magic, but he isn't going to hand over his crown to either of his sons until he gets exactly who he wants.