i found this theory on Lucas Wiki, but at first, this is not a desperate try to let him look innocent, it just seems really interesting.

I talked with @six-eyed-disaster about it and we expanded the theory a bit. :D

like the person above already said, we just got one mention of Oliver and that was from his journal entry. never we’ve seen something by Jack or Marguerite. Or a newpaper article about a little boy who was missing and later found dead on his classmates attic.
Or something mentioned by Zoe. they shared a room at this time and I doubt that Oliver was quite the whole time. He would have screamed.
So one reason where that thr Bakers where all involved and covered it up what would be pretty disturbing, even for that game.
OR the theory that Oliver was just, in fact, a imaginary friend.
Or Olivers Parents where the worst parents alive who never looked for their son. Oliver had mentioned it that he will be at Lucas Birthdayparty, if he hadn’t come home the Bakers where the first they had checked to. so far can’t he have starved.

I KNOW that the game is not about Lucas, but the Oliver entry was… kind of random? It was just thrown in and never mentioned again. Not even by Lucas who is actually really proud of his kills. He had mentioned it ‘You know Ethan, I killed already before all that.’. But we haven’t heared something like that.

And Jacks hesitation at mention that Lucas is no Killer could have also been because, maybe this Jack knew that Lucas was cured, but he knows about his sons mentality. that he’s still, even cured, not still sane.

It’s still just a theory.

what do you guys think? :)