Lmao, so many moral warriors here... I will be the first to admit they shouldn't get involved with each other, but if both parties involved no longer care it's not our place to get criticize. They just need to be aware that any relationship between the both of them might have tragic consequences for their children and or grandchildren. There is also a very negative social stigma if they get found out. If they do choose to be together, they should resolve themselves to those possibilities or it will end very badly for all involved. On a side note, if brother is just a horny lech who just wants to bang his sister because he thinks she's an easy target, tell her to knee him in the groin any time he comes near her. I know tasers are getting cheaper every day, some of the simple models are only are $20 - 30 usd
Ai-chan, this is fake, RIGHT? If this is real then I'm not sure what to do. If this is a novel then incest is win-cest If this is one of your fantasies than I could sigh in relief.
Gotta say though, I have sisters, the thought of looking at them like this would of made me , that shits nasty.
Actually admonishing them strictly at an early age would do boys a favor. So they didn't make mistakes with girl they're interested with and they didn't make dark spot in their own history. Trust me you don't want your big sister keep telling the girl you bought homes how you used to be interested in her panty or trying to peek her changing.
According to the fairytales I've been studying recently, she has two options. Option 1: She can tell him that she'll only be with him/let him touch her if he can bring her three things: a dress the colour of the sky, a dress more beautiful than the moon, and a dress more beautiful than the sun. If he gets that far, tell him she needs the skin of his favourite pet. If he gets that far, wrap those all up in a bundle and leg it - life as a hobo has got to better. Option 2: She asks him why he loves her and/or what he finds so attractive about her. When he (inevitably) boils it down to one body part, cut it off and give it to him on a gold platter - tell him he has no more reason to love/want her now! (Warning: this may result in being locked in a chest and thrown into the sea.) I understand, but this is Ai-chan talking. It's probably either a lewd dream, a hentai plot, or something for one of her novels (also lewd).
My best advice is they need counseling from their parents or whatever doctors. Plus they should also stay away from each other before its too late.