I want to ask the developer and gamer since there is so many incest game for me if the games is incest they should have blackmailing or forced its your mother or sister in every game the charachter is easy to nail she is not your girlfriend these game should be a little bit realistic
Being force or blackmailed is what define incest .
If there is game like this tell me
I'll not deny that many incest plots aren't the most plausible, with many just being grind and fuck. But there are definitely other ways to cause incest. My own script, which should finally be release soon, gives a psychological trauma that brings the twins together to be the impetus for their future consensual relationship. Many plots also use other more common methods, like the sisters/daughters you didn't grow up with becoming your lover because you don't have the psychological blocks that develop sometime around or just before puberty (I'm not exactly sure it was years ago that I read about this) that exists to stop us from fucking our families.
Now, being into blackmail and coercion in your porn isn't unheard of... personally I'd only really be into that if the protagonist is female, its written well, and she has a mind of her own, but if that's your thing it's out there. Sadly most developers can't write coercion to save their lives, so you get silly plots like the one in Man of the House or the many that exist in "retard in lechertown" games.