By taking the name John XXIII, he settled the question of whether the previous John XXIII was an anti-pope.
“By taking the name John XXIII, he settled the question of whether the previous John XXIII was an anti-pope.”
Since the original “John XXIII” willingly renounced any claims to the papacy and recognized Martin V it would seem that was taken care of in the 15th century. As a final jibe at Martin V, however, his supporters made sure that his tomb inscription said: “John the former pope”. Martin V was furious, but let it stand.