"Your brother is still a guy.... and he still has a cock.... so why wouldn't he fuck you? His cock can cum using you the same as if he was fucking any other girl, so why shouldn't he fuck you? If anything you should be encouraging him to fuck you..... a sister should look after her brother! ;)"
"And if you clean it all up.... she won't even know what you did! ;) Well, until she misses her period..... then she's really going to be confused!!! But that's ok, you can tell her you don't mind helping her raise the baby.... after all, isn't that what a good brother would do.... help his sister out... ;)"