In a pea pod:

Second-Born Royals have superpowers.

Secret Society of Second-Born Royals: protect and serve the monarchies.

Main villain: take down the monarchy; the people are citizens, not subjects.

Heroes: two adult and four teen second-born royals.

Villains: one adult and one teen second-born royal.

Ending: the villains are defeated, the monarchy continues its reign over its subjects.

Queen's promise: there will be a parliament added to the government.

Sequel: capture the escaped teen villain.

"Long live the Queen! Long live the monarchy!"