For the record though, I wouldn't blame the old owners too much for the mix up. When we bred rabbits for show, we would occasionally sell a buck or doe that wound up being visited by the magic faerie later on and ended up being the wrong sex.
Plus little males do tend to look like females when...
If you're breeding just for meat, I wouldn't sweat it if they're brother and sister. It's It'sn oopsie batch, happens more than you'd think unfortunately