So let me see if I got this right.
You can pick to be the Father or the Son as the MC.
If you pick the Father, the story is about the two daughters.
If you pick the Son, the story is about the mom.
No matter which you picked, the other story does not happen canonically, sisters don't sleep with dad, Wife doesn't fuck your son ect.. (Which is good because NTR is just the worst)
Eventually you can get the Mom or Sisters depending on your starting MC but it's not in game yet.
Do I have that right?
If so, this seems like 2 different stories being made at the same time making no one happy.
Seems like it would be faster to just proceed with one story to the end then go make the other using some old assets/some new assets.