Royal Bastards by Andrew Shvarts

Royal Bastards (2017) marks the newest addition to YA epic fantasy — a genre that seems to be having a bit of a moment. We meet Tilla, our plucky young heroine and bastard to the Lord Kent, and her half-brother Jax, swigging wine on the palace roof and watching the arrival of the visiting Princess Lyriana. Despite their royal blood, the bastards are worlds apart from the legitimate royals, though all that may be about to change…

A great feast marks the welcome for Princess Lyriana, but she shocks Tilla and her fellow bastards by sitting at their table, instead of with the highborns. That night, Tilla leads Lyriana and her fellow bastards on an evening escapade, but they find themselves witnessing a crime and a plan to start another Great War. Now Tilla and the bastards must run, taking Lyriana with them to protect the future queen of the kingdom.

Sequel...