With the incest patch he is, but he will not know that until after the DNA results which is quite far into the game.I have no idea what you're talking about. I quit and erased it after I heard the word "adoption". (In the intro, I guess)
So what's going on? Is the MC blood-related to his "family" or not?
Without the incest patch, he is adopted
In a way it is incest, just not blood related incest, if you decide not to use the incest patch