>>55443534That sounds like a funny series with a Monster... or well Kid of the Week gimmick. Every chapter a new kid born of fucked up circumstances comes back in time seeing the fucked up state of their parent's relationship and thinking they need to fix their it if they want to keep existing only to start fading away as the timeline erases them after altering their parents relationship for the better.
I could see it being done in two ways one as an anthology where it's the same scenario played by different chuuba kids in different circumstances. The other way as it being a harem fic that only grows larger as the kids born of one night stands and or desperation accidentally keep fixing everything.