Tethys and Okeanos are Rhea's siblings. They and their three thousand daughters, the Okeanides, were said to preside over the sources of earth's fresh-water. According to Homer, Tethys also took care of the young Hera after she had been disgorged by Kronos. It doesn't say exactly why Rhea left her daughter in Tethys's care, but in my version it probably was because Hera was exceptionally wild and unruly, and Rhea had four other children besides that who needed help to adjust after finally being brought out into the world. As a result, Rhea and Hera aren't that close. Hera rather sees Tethys as her mother.
Yeah, Athena has a lot of aunts, and uncles. By her maternal
Yeah, I can see Hera being too much.
And Oceanus and Tethys raised three thousand girls, so one Hera couldn’t have been hard.
But given their great marriage, despite being introverted, it gave Hera a desperate longing to have a marriage like theirs.