But why is Apatzec Intli IV calling his brother and sister “uncle and aunt” then?It's either because of the age gap or Atlacan and Caztaca are actually the children of Apatzec Intli III's father, who died not long before the events of the original Ixalan block.
The story describes it like this: "On the one side was Atlacan Huicintli, the boy-emperor's uncle and posthumously legitimized paper son of the late emperor."
So... it's also possible the family tree is a helix
