There exists two different Greek cosmogony. One where Khaos came first (Hesiod Theogony 116) But there is a version where Khronos came first and was the father of Khaos with Ananke. It shows that Gaea is the mother of Khronos. And yet, Gaea was the second to come into existence on her own after Khaos in the previously mentioned version and that Gaea was the one who made Ouranos. In another version, it shows Gaea is actually the mother of Khaos. Who came first? Help! Thank you. ;__;
The funny part about genealogies of the Gods is that they are all equally ‘correct’, as long as they stem from ancient sources. Genealogies of the Gods were all written down by humans about the Gods and there are a variety of them. Which one is entirely true is unknown and perhaps none of them are–or all of them. The most famous account of how the Gods came to be comes from Hesiod. His 'Theogogy’ is a complete recounting of the story, starting with Khaos:
“Verily at the first Chaos came to be, but next wide-bosomed Earth, the ever-sure foundations of all the deathless ones who hold the peaks of snowy Olympus, and dim Tartarus in the depth of the wide-pathed Earth, and Eros, fairest among the deathless gods, who unnerves the limbs and overcomes the mind and wise counsels of all gods and all men within them. From Chaos came forth Erebus and black Night; but of Night were born Aether and Day, whom she conceived and bare from union in love with Erebus. And Earth first bare starry Heaven, equal to herself, to cover her on every side, and to be an ever-sure abiding-place for the blessed gods. And she brought forth long Hills, graceful haunts of the goddess-Nymphs who dwell amongst the glens of the hills. She bare also the fruitless deep with his raging swell, Pontus, without sweet union of love. But afterwards she lay with Heaven and bare deep-swirling Oceanus, Coeus and Crius and Hyperion and Iapetus, Theia and Rhea, Themis and Mnemosyne and gold-crowned Phoebe and lovely Tethys. After them was born Cronos the wily, youngest and most terrible of her children, and he hated his lusty sire.” [ll. 116-138]
He goes on to list a great many deities, cutting out a rough shape of the cosmos while doing so. There are many variations of this family tree, and in the ancient writings, there are also creation stories that range beyond this basic framework. In the Orphic Theogonies, for example, the universe does not start with Khaos, but with Thesis and Hydros, reaching back to Hómēros:
“Originally there was Hydros (Water), he [Orpheus] says, and Mud, from which Ge (the Earth) solidified: he posits these two as first principles, water and earth … The one before the two [Thesis], however, he leaves unexpressed, his very silence being an intimation of its ineffable nature. The third principle after the two was engendered by these–Ge (Earth) and Hydros (Water), that is–and was a Serpent (Drakon) with extra heads growing upon it of a bull and a lion, and a god’s countenance in the middle; it had wings upon its shoulders, and its name was Khronos (Unaging Time) and also Herakles. United with it was Ananke (Inevitability, Compulsion) , being of the same nature, or Adrastea, incorporeal, her arms extended throughout the universe and touching its extremities. I think this stands for the third principle, occuping the place of essence, only he [Orpheus] made it bisexual [as Phanes] to symbolize the universal generative cause.” [Theogonies Fragment 54] So I can’t point you to one account that is entirely accurate. At best, I can tell you that many of the ancient writers had their own thoughts on the subject, undoubtedly inspired by the community they lived in, the region they lived in, and the circles they moved in. Not knowing everything about the Gods is just one way by which They let us know we’re mere moral beings, I suppose. Embrace it!