Short answers, pulled from the story.
Hesiod states that Uranus and Gaia were the parents of Tethys. Plato in his Timaeus provides genealogy possibly Orphic showing Uranus and Gaia as parents of Oceanus and Tethys who then birthed Cronus Rhea Phorcys and other Titans.
Hesiod states there were three thousand river gods springing from their union. Three thousand Oceanids also descended from them including Metis Eurynome Doris Callirhoe Clymene Perseis Idyia and Styx.
Passages in book 14 of the Iliad called the Deception of Zeus suggest Homer knew traditions placing Oceanus and Tethys as primeval parents rather than Uranus and Gaia. Hera describes the pair as Oceanus from whom gods are sprung and mother Tethys while claiming they lovingly nursed her in their halls during Zeus's deposition of Kronos.
By fourth century AD iconography began merging with Thalassa Greek personification of sea. Such blending consistent with poetic naming conventions emerging throughout Hellenistic period where abstract concepts gained concrete divine forms through metaphorical language used by writers across centuries.
Earliest mosaic decorated triclinium overlooking pool excavated House Calendar Antioch dated shortly after AD 115 now housed Hatay Archaeology Museum 850. Additional pieces exist Shahba Museum in situ Baltimore Museum Art 1937.118 Memorial Art Gallery 42.2 and public bath installed Boston Massachusetts Harvard Business School Morgan Hall formerly Washington DC Dumbarton Oaks 76.43.