Apparently, boys are not nearly as interested in being princes as girls are in being princesses. I'd look for more books, but there's a wedding on.
Yolen, Jane. Prince Across the Water.
"In 1746, a year after the Scottish clans have rallied to the call of their exiled prince, Charles Stuart, to take up arms against England's tyranny, fourteen-year-old, epileptic Duncan MacDonald and his cousin, Ewan, run away to join the fight at Culloden and discover the harsh reality of war. "
Wyatt, Melissa. Raising the Griffin.
"When the people of Rovenia vote to restore their monarchy, sixteen-year-old Alex Varenhoff must suddenly leave his native England to become prince of a land he knows only from his grandfather's stories. " (This is sort of a princess diaries for guys, with a lot more action and intrigue.)
Burnham, Niki. Royally Jacked.
"Valerie, caught in the middle of her parents' divorce, opts to stay with her father who has just accepted a job as protocol chief for some European royals, but she is beginning to think she has made the wrong choice until she meets the prince. " (This is part of a three book series, and one of the Simon Pulse Romantic Comedies.)
O'Connell, Tyne. Pulling Princes.
"Includes glossaries of British slang and fencing terms. Hoping to become more popular at her English boarding school, fifteen-year-old Californian Calypso Kelly invents a fake boyfriend, until she realizes that her wit and skill at fencing may be enough to attract the attention of a real-life prince. "