A King Ensnared - The Stewart Chronicles, #1

James, 12-year-old heir to the throne of Scotland, is in mortal danger. His father, King Robert III, is dying, and Robert's half-brother, the Duke of Albany, is plotting to seize power. The duke has already murdered James' older brother, and James will be next. James escapes Scotland and the murderous duke. Captured and imprisoned by the English, he grows to be a man of contradictions: a poet yet a knight, a dreamer yet fiercely driven.
Hardened by his years in the Tower of London and haunted by his brother's brutal murder, James is determined to regain his freedom and end the Duke of Albany's misrule. But King Henry of England is determined that to pay for his freedom, James must betray Scotland and everything he believes in.