Palace eunuchs

Am wondering about the utility of eunuchs in Imperial China. I suppose you could trust them around the concubines and female members of the dynasty, and their low social status made them expendable and dependent on you. Plus they wouldn't be sitting around scheming about establishing their own dynasty. But apparently your average eunuch could not always control urination, and tended to carry a "sickly sweet" smell.

In my Korean step-family, I sometimes hear stories about half brothers and sisters, who are the children of concubines. Makes the family tree a bit complicated.