OMG!!

siblings*

(-_-") are you even reading this manga
Wait till you find out the king has a look alike

I know that he have a look alike, so you mean she might be the real king's sister??!
but the real king is always hidden cuz he have a weak body, so how come the other guy know about that? when she said the only other person who knows that song was her brother!!

I already knew one of them was the brother but I'm still not sure which one I mean the king could have play that song in front of him before so I'm pretty sure it could go either way

I thought it was said at one point that he was an adopted brother. Can't remember for sure since it's been a long time since I've read most of this

They arent real bloodsiblings, Hisui family found the substitute king and pretty much just took him in until one day he was kidnapped and ever since they never saw him again till.now.