I don't think I quite follow. Since when is Basen posing as an eunuch? He's not working in the inner palace like Jinshi, so there would be no reason for him to be one.
From my understanding, Rakan knows Jinshi's identity (the imperial brother) just because he's that "perceptive" or whatever do...
Jinshi doesn't know he's the current Emperor's son.
In the past he thought that he is, but it changed after his meeting with the former Emperor (iirc, someone can correct me if I'm wrong).
OKAY i think it's time to make things clear for some people because some cannot read and/or are too lazy to check suff before saying something stupid or false: MAOMAO IS 17 at the beginning of the story, while JINSHI IS 18. From CHAPTER 34 we know that Jinshi's currently the same age as Basen...