chapter 7 where the whole party scene takes place and even then it could be skirted pretty easily with assumption no one even knew she had a brother who has been missing for the best part of a decade that she very likely never spoke about much and certainly not to fated rivals and boys she was never interested all that much in getting close to in the first place.
Even if we overlook the party scene there is the glaring plot hole of why Monica never tried to get in touch.
In the canon game it's because she had no rights, she wasn't his mother so what's her excuse when she is his mother and does have rights?
Why are the girls never mentioned by the dad?
The man screwed over everyone in his life from the MC's mother to Monica, to Elaine to Bella and anyone he comes into contact with. He was the very definition of a complete bastard. So he conveniently forgets he has daughters?
Why are they not in the will?
Why did Monica not contend child support like his actual mother did, it would have solved all her financial problems.
Why is she not contending the will, she has the right as his ex wife?
Elaine never married him so the only one with both children and family ties would be an incest modded Monica.
They do various things in public and incest is still taboo in that world so why are the people fighting to get his dads money not using the fact he's committing illegal acts against him?
The very plot of the game instantly becomes riddled with massive plot holes when trying to make them family.
I'm not trying to bash at you, I know you aren't asking for incest but Cheeky didn't set it up to be patched into an incest game so it takes a turn to nonsense when people try. There is only so much of the story a mod can change, it can't change the plot.