Spoiler...
Well his brother will be filled in, after the plague arc. He is comming back to the pharmacy and falma have to tell him. His brother doesn't take him seriously at first if I remember correctly.
Where did you read it? Or is it s novel could you please link it?!! Please
Its on novelupdates.com, by the same name
So ... very late reply ... sorry (￣∇￣lll)
I read it there https://ncode.syosetu.com/n8541cr/ but it's not translated. There are chapters on novelupdates but there aren't much of them yet.
Am I the only one here who thinks it sucks the fact falma keeps hiding things from his older brother. It’s annoying how his big bro trusts him and acknowledges him and yet so many know things abt falma and his brother is just completely left out.