Primordial Three
Apollo, Cybele and Dionysus are not a divine family. They are three incompatible answers to non-being - Harmony, Structure and freedom - and each answer creates the failure the next must inherit.
Three Answers to Nothing
Aurelion's oldest cosmology has no single creator enthroned above the world. It begins instead with the Great Nothing and three formulas for resisting it. The gods are less like sovereign personalities than operating principles that became mythic persons in later religion. Their peoples are extensions of those principles: not merely worshippers, but instruments through which a divine answer was tested upon reality.
Apollo is the answer of Harmony, form and law. The elves are described as his thought made active: a network able to command rivers, forests, mountains and elemental forces because they did not stand outside nature as users of it. Their perfection was also their weakness. Where there is no meaningful alternative, there is no Will. Harmony reduced disorder so completely that the world answered with the Riot of Nature; the network became self-sufficient, and the civilization that had mastered the environment dissolved into it.
Cybele is the answer of Structure. The Great Spider does not persuade chaos to become harmonious; she gives it matter, limits, formulas and machinery. Dwarven cities became workshops large enough to resemble countries, and dwarven identity became inseparable from tools, equations and function. Their catastrophe was the mechanical version of the elven one. The systems built to preserve form outlived the people who built them, until the makers were fixed into the very machinery meant to defend them.
Dionysus introduces the principle neither elder answer could safely contain: personal Time. He is passion, multiplicity and the ability to choose otherwise. Humans are therefore weaker, noisier and less stable than elves or dwarves, but they are the first people whose Function is not necessarily destiny. That freedom makes Soul possible. It also makes greed possible, and from greed comes the golden heresy that turns blood into metal. The Three are thus not a ladder of better gods. They are three increasingly dangerous experiments in how existence might refuse the Great Nothing.