What kind of brother would say this?! A teenager one at that! I don't think he is thinking at all about being in that position at all.
Edit: i have to put this because people are getting what i meant wrong. So to any future readers this is what i meant.
I meant what the MC said about boasting about it online. MC isn't thinking of what the brother would be going through because of this at all. With the brother being a teenager he is probably being teased or bullied about his sister's job. He is probably getting fake friends that are just aiming to F his sister thinking that she is easy. But the MC is not taking any of that into account or even thinking about that...not even once. He is only thinking from a "i know and interact with a gravure idol" standpoint and not a "gravure idol's teenage brother around other teenagers" standpoint.