Here the patch will rather harm. How do you imagine the story will look like MC's father marries MC's mother while having adult children? Not only that, the woman's daughter should then be MC's twin. This will rather break the entire logic of the game.
with some clever dialogue replacement - quite easy
they were family before (daughter is MC's sister, woman is mother), but got divorced and separated years ago, while kids were still too young to built any connection/memories, father took son, mother took daughter
years later, present time, they found each other again (could be even by accident) and decided to give it another shot, things are going well, so they are back together again (although due to years apart they may as well be strangers starting fresh)
i know sounds like a stretch from first glance, i'm not a fucking writer, but it's not unique setup either
there are some incest games where included i-patch results in similar backstory, written to work both with and without patch