The Council of Constance 1414-18 had the main purpose of ending the Three Popes Schism, and was convened by the Antipope John XXIII. John had two brothers who were sentenced to death for what?
Antipope John XXIII Angevin-Neapolitan war. His two brothers were sentenced to death for piracy by Ladislaus of Naples. He studied law at the University of Bologna and obtained doctorates in both civil and canon law. Probably at the prompting of his family, in 1392 he entered the service of Pope Boniface IX, first working in Bologna and then in Rome. (The Western Schism had begun in 1378, and there were two competing popes at the time, one in Avignon supported by France and Spain, and one in Rome, supported by most of Italy, Germany and England.) In 1386 he is listed as canon
Western Schism succeeded by antipope John XXIII, who won some but not universal support. Finally, a council was convened by Pisan antipope John XXIII in 1414 at Constance to resolve the issue. This was endorsed by Pope Gregory XII, thus ensuring the legitimacy of any election. The council, advised by the theologian Jean Gerson, secured the resignations of John XXIII and Pope Gregory XII, who resigned in 1415, while excommunicating the second antipope, Benedict XIII, who refused to step down. The Council elected Pope Martin V in 1417, essentially ending the schism. Nonetheless, the Crown of Aragon did not recognize Pope Martin