I've played it now and can offer my 2 cents. It's certainly different and exploring some uncharted territory. If there was some more attention to detail and some more planning behind the script, it could be much more impactful.
The problems I see are mainly in the tone, pacing, and the MC.
Tone. It can't quite settle on a tone. The subject matter is extremely dark. It's probably one of the more fucked up situation we can find in a porn game that tries to keep a semblance of realism. It would likely benefit from a more consistent tone that captures the dire and abhorrent conditions the family has been put through. Dread, anger, hopelessness, fear, sadness, coping, perseverance, depression, trauma. These are some of the terms that spring to mind when considering the subject of this game in a realistic setting, but the game takes a rather nonchalant approach. The way it's presented now doesn't put nearly enough weight to the atrocities that are coming to light. This issue isn't helped at all by the possible choices at the MC's disposal.
MC. This could be the most glaring issue at this point. The rapey actions that the MC can take cannot be justified at all by his characterization thus far. He is all intent on protecting his family and saving them from Big John. He is sorry about the things he was forced to do as a child and the things he had forgotten. Yet, he can sleep rape his mom and sis, and coerce the youngest one into sexual acts. There is nothing in the script that reconcile this discrepancy. More care needs to be put into the code to create a viable path towards a rapey MC. His intentions and motivations need to change to match the choices he makes. If you are rapey, the MC should frame his battle against Big John as a way to claim the girls for himself. "These bitches are mine!" There is some established backstory that makes this possible already. MC was abused as a child just like the others. He could have a warped mind due to this ordeal.
And finally, the pacing has some big problems. This is a prologue, and a very short one at that, but you've already dropped incredible bombs that would have been better served as something that is insidiously brewing in the background. It could have explored the missing memory and the true nature of their situation over the course of a few updates. The situation with Maria(?) also seems extremely rushed. We went through an entire arc resulting in reconciliation in the span of like 10 minutes.
Other than those 3 points, there are oddities in the plot and character actions that don't seem too logical. Dissociative amnesia is not unheard of, but how come nobody explored their experiences with him until now? If he was being abused by himself in a controlled environment, I can see that he might keep it buried. In a household of this many people with everyone having gone through some fucked up shit, it seems quite unlikely that this whole situation is just coming to light right now. Also, is there no safety nets for abused foster children? I'm not an expert, but calling CPA seems like the logical thing to do as soon as any of the kids became old enough to understand the gravity of what they went through.
That's my 2 cents for what it's worth. Good luck. I do appreciate any dev that tries to tell a unique story.