See, the fact that the sister got pregnant is what made me give this a try. I LOVE breeding themes, but by the time it comes up...I am just throwing in the towel.
IF the impregnation had been done better, it could have carried the story on that alone. Give me some X-rays of the sperm fertilizing the ovum. Or the sister throwing up at some points, with hints at what is to come. Give me some sort of titillation rather than the "welp, sis is now pregnant" that we got. What the game ended up giving us was the kink of unsafe sex, NOT breeding when it felt like it was trying to do the latter.
If, saaaaay, abortion kinks were in play, it would work as is. It would make it fun to be an irresponsible little shit who came in his sister raw because he could always just abort whatever brat he made. The lack of attention to the breeding details would be a feature in that case, rather then a problem. Yes, it's ugly, but that's how you play THAT kink to the hilt.
Of course, none of this would be a true issue if it was paced better. Freaking grind...