We don't have Estarossa's birthday, which is why technically it's possible they share it, or it can be seen as a spoiler of some sort.Mel and estarrosa share a birthday? That is new to me lol.
My crackpot theory is that the demon king is actually the 10 commandments within each demon. Basically the demon king split himself and his power across the 10 commandments as both the means to control them and give them power to destroy their enemies. Of course, merely defeating a commandment is probably not enough to destroy the demon king.
I think zeldris is the leader of the commandments in the same way meliodas is the leader of the sins. Mel has only questionable and certainly irregular authority over the sins after all. And you have escanor who is a presumably greater powerhouse among them and also merlin who does not hesitate to take a leadership role among the sins if the situation calls for it. We saw how zeldris could not simply order galan not to go to camelot for instance a while back for instance.
We have both Mel and Zel's birthday, but not Estarossa's. It's fishy to say the least.
Yep I also think that, so if they kill all the commandments the DK would be resurrected basically. And I'm leaning more towards Estarossa being the leader, but not in the conventional way. He doesn't have an active role, and Zel is more on the front when it comes to managing the TCs affairs. So while Zel fits the role of a leader better, I think it's just like day Escanor or Merlin and Mel, in the sense that they're more serious and are even seen leading, but it's Mel the actual leader and he's more of the "silent" type that doesn't let his intentions known, and Estarossa is the same.