Many popular portrayals of ancient kingdoms & harems include eunuchs who prototypically act as advisors to the king but oftentimes slip into intrigue & politics. How legitimate are these depictions? How common were eunuchs & why were they castrated? What was daily life like for a eunuch? How long did the eunuch model exist?
So that's a lot of questions! Did you have any culture in particular in mind or just thinking about Game of Thrones? If it's just idle wondering s I'll dig up some old things I've written for you, but otherwise, eunuchs have existed in a lot of times and places!