After the Treaty of Coruscant that ended the Great Galactic War and Alderaan's subsequent withdrawal from the Galactic Republic, the Crown prince of Alderaan, Gaul Panteer—who personally withdrew Alderaan from the Republic in protest over the treaty—was assassinated; the queen died a few days later.
With no monarch and no heir, the parliament was tasked with deciding which of Alderaan's noble houses would inherit the throne. The legislature became deadlocked, leading one of the houses to decide to settle the matter by force. This house's actions led to one of the bloodiest civil wars in galactic history.