Human rulers die, and the next generation takes over. Sometimes the older generation gets “helped” off the throne, either by assassination or war. So it’s not surprising that mythology has many versions of this succession story, which rarely involve peaceful inheritance.
The main solar deity of Mesopotamia was certainly male – Šamaš in Akkadian, and UTU in Sumerian. Evidence for this figure is abundant, and he performs normal sun-god/dess activities like witnessing and judging human activity, and maintaining life.
However, there are early personal names with a more feminine connotation, such as Ummi-Samas, (Šamaš is my mother), and Tulid-Shamash (Šamaš gave birth), which indicate that perhaps Šamaš had a female side. (In the same region, after all, the Canaanites and the Arabs both had sun-goddesses, Šapaš and Shams.)