are Olivia and graham cameos, their backstory sounds its a different game entirely
I don't believe so but their models are used in a lot of other VNs.
Funny enough, their storyline is such a problem for me that I made my first ever Renpy VN doing a rework/side story of those two, F and D.
It was pretty just a learning effort so I'd clean it up a lot before ever sharing it but it was technically my first ever. Anyway...
That's how odd their treatment is so I can see why someone may think they're cameos. Graham specifically is written all over the place as far as what he wants, likes and such. In my short story he has a goal or plan with not only his daughter but those two and F/D.