Yet the unnamed author I mentioned effectively had a long term health issue. It wasn't especially well known, but neither it was hidden.
Well, not all families have a hypocritical relationship you know. Both my son and daughter know that I'm, slowly, working on an adult game ; my daughter even lecture me time to time because I'm too slow. It's called being honest, supportive, and, yes, also open minded.
Anyway, having taboo subjects in a family is the opposite of a healthy relationship. It don't mean that all authors have to tell it to their whole family, just that there's no reason, out of purely personal ones, to not do it.
And since they are both adults and I raised them, I know that they understand that I'm just making a game, and that it's nothing more than a hobbit. Therefore, even if it was about a father having an incest relationship with his daughter, perhaps that it would make her uneasy, but she still would know that it have nothing to do with an untold desire of mine.
You should tell your friend that he have some anger issues.