I know. But the MC's current situation is very dire, so adding her brother in causes the MC to be on a defense and cautious mode in her words and actions which will force her to obey the emperor's words even more.
For example, if MC dares to fail at her task or tries to kill the emperor, MC's brother might get his fingers or fingernails pull out or something as punishment.
If it were only the MC there in the first place, she would have no trouble coming up with a good plans while the emperor is cautious of the MC.
Yes, it is clear that MC need her brother for her conquer quest, but will that even matter if her creations can easily take over the whole empire, even if the people apposed, they will lose anyways because of the firearms the MC has.
well it isn't the brother's fault though, do you think he wanted this to happen or something?! it Cain fault if anything, not the brother!╮( ̄▽ ̄)╭ and try to get how he feels too. he also wants to help his sister in this and come back home with her safe or stay with her there. how can you just leave your family when you see them in danger?!
yeas it is matter, they need a reason to go against the emperor, like it or not! they need her brother there!

...Am I stupid or can't the MC's brother just fuck off by saying this world is a novel to someone or anyone.. then he would have teleported to the real world and wouldn't be a burden to the MC...